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Mineralogy Petrology

Dr. Dávid, Árpád

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Mineralogy Petrology Dr. Dávid, Árpád

Publication date 2011 Szerzői jog © 2011 EKF

Copyright 2011, EKF

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Tartalom

1. Mineralogy Petrology ..................................................................................................................... 1 1. Definition of a mineral .......................................................................................................... 1 2. Classification of Minerals .................................................................................................... 1 3. Crystals and Crystal Systems ................................................................................................ 2 4. Crystal forms ......................................................................................................................... 6 5. Crystal habits ......................................................................................................................... 7 6. Twinning in Crystals ............................................................................................................. 8 7. Physical characteristics of minerals ...................................................................................... 9 8. Inclusion in minerals ........................................................................................................... 12 9. Pseudomorphs ..................................................................................................................... 13 10. Mineral occurrences and environments ............................................................................. 13

10.1. Igneous minerals ................................................................................................... 13 10.2. Sedimentary minerals ........................................................................................... 14 10.3. Metamorphic minerals .......................................................................................... 14

11. IGNEOUS ROCKS ........................................................................................................... 16 11.1. Classification ........................................................................................................ 16 11.2. Basic classification scheme for igneous rocks on their mineralogy mineralogy .. 17 11.3. Mineralogical classification .................................................................................. 17 11.4. Chemical classification ......................................................................................... 18 11.5. Magma evolution .................................................................................................. 19 11.6. The most important igneous rocks and their components ..................................... 20

12. SEDIMENTARY ROCKS ................................................................................................ 22 12.1. Clastic sedimentary rocks ..................................................................................... 23

12.1.1. Conglomerates and breccias ..................................................................... 25 12.1.2. Sandstones ................................................................................................ 26 12.1.3. Fine-grained sedimentary rocks ............................................................... 27 12.1.4. Mudrocks ................................................................................................. 27

12.2. Carbonate rocks .................................................................................................... 28 12.2.1. Components of the limestones ................................................................. 28 12.2.2. Classification ............................................................................................ 29 12.2.3. Terrestrial limestones ............................................................................... 30 12.2.4. Other calciferous rocks ............................................................................ 31

12.3. Mixed rocks .......................................................................................................... 31 12.4. "Other" sedimentary rocks .................................................................................... 31 12.5. Volcanoclastites .................................................................................................... 31

12.5.1. Classification of pyroclastites on the base of grain size ........................... 31 12.5.2. Arise of pyroclastites ................................................................................ 32 12.5.3. Pyroclastic surges: ................................................................................... 32

13. METAMORPHIC ROCKS ............................................................................................... 33 13.1. Limits of metamorphism ....................................................................................... 34 13.2. Metamorphic rocks and index minerals ................................................................ 34 13.3. Some mechanism of methamorpism ..................................................................... 34

13.3.1. Foliation ................................................................................................... 34 13.3.2. Chemical reactions ................................................................................... 35

13.4. Some types of metamorphism .............................................................................. 35 14. Local metamorphism: ....................................................................................................... 35

14.1. Texture of metamorphic rocks .............................................................................. 36 14.2. Classification of metamorphic rocks .................................................................... 36 14.3. Metamorphic Facies ............................................................................................. 37 14.4. Protolith ................................................................................................................ 38 14.5. Metamorphic rocks with characteristic texture ..................................................... 38 14.6. Rocks of contact metamorphism ........................................................................... 39 14.7. Retrograde metamorphism .................................................................................... 39

15. Geology of the Mátra Mountains ...................................................................................... 41 16. 1st stop: Verpelét, Vár Hill, volcanic cone ....................................................................... 42 17. 2nd stop: Domoszló, Tarjánka Gorge ................................................................................ 43

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18. 3rd stop: Gyöngyös, Farkasmály quarry ........................................................................... 44 19. 4th stop: Gyöngyössolymos, Bábakő ................................................................................ 45 20. 5th stop: Gyöngyössolymos, Kis Hill ................................................................................ 46 21. 6th stop: Gyöngyöstarján, Köves Hill ............................................................................... 47 22. 7th stop: Gyöngyöstarján, Füledugó quarry ...................................................................... 49 23. 8th stop: Szurdokpüspöki, diatomite quarry ...................................................................... 50 24. Dunabogdány, Csódi Hill .................................................................................................. 51 25. Erdőbénye, Mulató Hill, andesite qarry ............................................................................ 53 26. Felsőcsatár, greenschist quarry ........................................................................................ 55 27. Kisnána, andesite quarry ................................................................................................... 57 28. Pálháza, perlite quarry ...................................................................................................... 59 29. Rudabánya, iron ore quarries ............................................................................................ 61 30. Salgótarján-Somoskőújfalu, Eresztvény basalt quarry ...................................................... 63 31. Sukoró, Rigó Hill, granite quarry ...................................................................................... 65 32. Szarvaskő, Újhatár Valley, Tóbérc-Mine, gabbró quarry ................................................. 66 33. Szokolya-Királyrét ............................................................................................................ 69 34. Tapolca, Halyagos Hill ...................................................................................................... 71 35. Telkibánya, mine dump of Vörösvíz drift gallery ............................................................. 73

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1. fejezet - Mineralogy Petrology

BASICS OF MINERALOGY

1. Definition of a mineral

A mineral is a naturally-occurring, homogeneous solid with a definite, but generally not fixed, chemical

composition and an ordered atomic arrangement. It is usually formed by inorganic processes.

Let's look at the five parts of this definition:

1.) "Naturally occurring" means that synthetic compounds not known to occur in nature cannot have a mineral

name. However, it may occur anywhere, other planets, deep in the earth, as long as there exists a natural sample

to describe.

2.) "Homogeneous solid" means that it must be chemically and physically homogeneous down to the basic

repeat unit of the atoms. It will then have absolutely predictable physical properties (density, compressibility,

index of refraction, etc.). This means that rocks such as granite or basalt are not minerals because they contain

more than one compound.

3.) "Definite, but generally not fixed, composition" means that atoms, or groups of atoms must occur in specific

ratios. For ionic crystals (i.e. most minerals) ratios of cations to anions will be constrained by charge balance,

however, atoms of similar charge and ionic radius may substitute freely for one another; hence definite, but not

fixed.

4.) "Ordered atomic arrangement" means crystalline. Crystalline materials are three-dimensional periodic arrays

of precise geometric arrangement of atoms. Glasses such as obsidian, which are disordered solids, liquids (e.g.,

water, mercury), and gases (e.g., air) are not minerals.

5.) "Inorganic processes" means that crystalline organic compounds formed by organisms are generally not

considered minerals. However, carbonate shells are minerals because they are identical to compounds formed by

purely inorganic processes.

An abbreviated definition of a mineral would be "a natural, crystalline phase". Chemists have a precise

definition of a phase:

A phase is that part of a system which is physically and chemically homogeneous within itself and is surrounded

by a boundary such that it is mechanically separable from the rest of the system.

2. Classification of Minerals

Minerals are classified on their chemistry, particularly on the anionic element or polyanionic group of elements

that occur in the mineral. An anion is a negatively charge atom, and a polyanion is a strongly bound group of

atoms consisting of a cation plus several anions (typically oxygen) that has a net negative charge. On the base of

this, mineralogy knows 10 classis of minerals:

Class of minerals Characteristic anion

1. Native elements -

2. Sulphides S2-

3. Halides F-, Cl-, Br-, I-

4. Oxides, hydroxides O2-, (OH)-

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5. Carbonates, nitrates [CO3]2-, [NO3]-

6. Borates [BO3]3-, [BO4]5-

7. Sulphates [SO4]2-

8. Phosphates, arsenates, vanadates [PO4]3-, [AsO4]3-, [VO4]3-

9. Silicates [SiO4]4-

10. Biogenic minerals -

3. Crystals and Crystal Systems

The unit cell of a mineral is the smallest divisible unit of a mineral that possesses the symmetry and properties

of the mineral. It is a small group of atoms, from four to as many as 1000, that have a fixed geometry relative to

one another. The atoms are arranged in a "box" with parallel sides called the unit cell which is repeated by

simple translations to make up the crystal (Fig. 1.1., 1.2.).

Fig. 1.1. Evolving of lattice by three dimensional translation of lattice points

The atoms may be at the corners, on the edges, on the faces, or wholly enclosed in the box, and each cell in the

crystal is identical. This is what was meant by an "ordered internal arrangement" in our definition of a mineral.

It is the reason why crystals have such nice faces, cleavages, and regular properties. The box of the unit cell is,

in general, a parallel-piped with no constraints on the lengths of the axes or the angles between the axes.

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Fig. 1.2. The unit cells

The box is defined by three axes or cell edges, termed a, b, and c and three inter-axial angles alpha, beta, and

gamma, such that alpha is the angle between b and c, beta between a and c, and gamma between a and b. The

presence of internal symmetry in the unit cell may place constraints on the geometry of the unit cell. The

different kinds of symmetry possible place different constraints on the unit cell geome tries giving rise to

characteristic cell geometries for each of the 7 Crystal Systems and 32 Crystal Classes:

Triclinic System: The triclinic system is the lowest symmetry system and contains only two symmetry classes.

One class contains only a center and the otherclass is left with no symmetry what so ever. All crystallographic

axes are inclined with respect to each other, with no angles equaling 90 degrees. Also all three axes are of

differing lengths (Fig. 1.3.). Classes of this system are parallellohedron and monohedron. The most important

minerals in this system: kaolinite, rodonite and turquoise.

Fig.1.3. Triclinic crystal axes

Monoclinic System: The monoclinic system is the largest symmetry system with almost a third of all minerals

belonging to one of its three classes. This system contains two non-equal axes (a and b) that are perpendicular to

each other and a third axis (c) that is inclined with respect to the ‘a’ axis (Fig. 1.4.). Classes of this system are

prism, sphenoid and dome. The most important minerals in this system: gypsum, azurite, native copper,

malachite, orthoclase, talc and mica.

Fig. 1.4. Monoclinic crystal axes

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Rhombic System: The rhombic system is based on three unequal axes all at right angles to each other. As can be

imagined, as one views down every one of the axes, two unequal axes crossed at right angles can be seen. A

possible two fold rotational symmetry is seen in the axes as well as two possible mirror planes that are parallel

to the axes (Fig. 1.5.). Classes of this system are rhombic dipyramid, rhombic disphenoid, rhombic pyramid and

rhombic dipyramic. The most important minerals in this system: aragonite, barite, marcasite, olivine, mica.

Fig. 1.5. Rhombic crystal axes

Tetragonal System: The tetragonal system is the least populated by natural crystals of all the crystallographic

systems. All angles between the crystallographic axes are 90 degrees but one of the three axes is longer or

shorter than the other two (Fig. 1.6.). Classes of this system are tetragonal pyramid, tetragonal dipyramid,

tetragonal trapzohedron, ditetragonal pyramid, ditetragonal dipyramid, tetragonal disphenoid and tetragonal

scalenohedron. The most important minerals in this system: zircon, chalcopyrite, cassiterite and rutile.

Fig. 1.6. Tetragonal crystal axes

Trigonal system: The trigonal system likewise has a threefold rotational axis or a threefold rotoinversion axis.

Although the six fold rotoinversion axis produces a trigonal looking crystal, that symmetry is produced by the

six fold symmetry operation (Fig. 1.7.). Classes of this system are pyramid, rhombohedron, trapezohedron,

ditrigonal pyramid, ditrigonal scalenohedron, dipyramid and ditrigonal dipyramid. The most important minerals

in this system: liver ore, dolomite, calcite, corundum, quartz and siderite.

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Fig. 1.7. Trigonal crystal axes

Hexagonal System: The hexagonal system is uniaxial, meaning it is based on one major axis, in this case a six

fold rotational axis, that is unique to the other axes (Fig. 1.8.). Classes of this system are pyramid, dipyramid,

trapezohedron, dihexagonal pyramid and dihexagonal dipyramid. The most important minerals in this system:

apatite, graphite, quartz, molibdenite and nepheline.

Fig. 1.8. Hexagonal crystal axes

Isometric System: The isometric system is the most symmetrical system possible in three dimensional space. It

is composed of three crystallographic axes of equal length and at right angles to each other (Fig. 1.9.). Classes of

this system are hexoctahedron, gyroid, hextetrahedron, diploid and tetartoid. The most important minerals in this

system: fluorite, galena, granates, diamond, halite, pyrite, native copper, sphalerite.

Fig. 1.9. Cubic crystal axes

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4. Crystal forms

A crystal form is a set of faces which are geometrically equivalent and whose spatial positions are related to one

another according to the symmetry of the crystal. If one face of a crystal form is defined, the point symmetry

operations which specify the class to which the crystal belongs also determine the other faces of the crystal

form. A simple crystal may consist of only a single crystal form. A more complicated crystal may be a

combination of several different forms. All forms which occur in a crystal of a particular system must be

compatible with that crystal system (Fig. 1.10.).

Fig. 1.10. The most common primitive crystal forms

Open forms

Pedion: consists of a single face which is geometrically unique for the crystal and is not repeated by any set of

symmetry operations.

Pinacoid: consists of two and only two geometrically equivalent faces which occupy opposite sides of a crystal.

The two faces are parallel and are related to one another only by a reflection or an inversion.

Dome: the two faces are related only by reflection across a mirror plane.

Sphenoid: the two faces are related instead by a 2-fold rotation axis then the dihedron

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Prism: is composed of a set of 3, 4, 6, 8, or 12 geometrically equivalent faces which are all parallel to the same

axis. Each of these faces intersects with the two faces adjacent to it to produce a set of parallel edges. The

mutually parallel edges of all intersections of the prism sides then form a tube.

Pyramid: is composed of a set of 3, 4, 6, 8, or 12 faces which are not parallel but instead intersect at a point.

pyramids is divided into two mirror-image faces which occupy an oblique angle with respect to one another.

Dipyramid: is composed of two pyramids placed base-to-base and related by reflection across a mirror plane

which runs parallel to and adjacent to the pyramid bases. The upper and lower pyramids may each have 3, 4, 6,

8, or 12 faces; the dipyramidal form therefore possesses a total of 6, 8, 12, 16, or 24 faces.

Trapezohedron: a closed crystal form possessing 6, 8, or 12 trapezoidal faces.

Scalenohedrons and rhombohedrons

Scalenohedron: consists of 8 or 12 faces, each of which is a scalene triangle. The faces appear to be grouped

into symmetric pairs.

Rhombohedon: possesses six rhombus-shaped faces.

Disphenoid: Members of the orthorhombic and tetragonal crystal systems produce rhombic and tetragonal

disphenoids, which possess two sets of nonparallel geometrically equivalent faces, each of which is related by a

2-fold rotation.

Crystal forms of isometric system

Cube: The cube is familiar to everyone as a symmetrical six sided box.

Octahedron: The octahedron is a symmetrical eight sided shape that may look like two four sided pyramids

lying base to base.

Rhombic dodecahedron: The dodecahedron has twelve rhombic sided.

Tetrahexahedron: This form is composed of 24 triangular.

Deltoidal tetrahedron: This form is composed of 24 deltoidal faces.

Hexoctahedron: The hexoctahedron is a richly faceted form with a total, if fully formed, of 48 triangular faces.

Tetrahedron: The tetrahedron has only four equilateral triangular faces (unless modified), four points and six

edges and when sitting on one face looks like a trigonal pyramid.

Pentagonal dodecahedron: The tetartoid is a 12 sided form that is very rarely seen. The faces are asymmetrical

pentagons.

Tristetrahedron: The tristetrahedron has 12 faces that are shaped like extremely acute isosceles triangles.

Deltoidal dodecahedron: The deltoid dodecahedron has four sided delta shaped faces.

5. Crystal habits

Crystal habit is a description of the shapes and aggregates that a certain mineral is likely to form. Often this is

the most important characteristic to examine when identifying a mineral. Although most minerals do have

different forms, they are sometimes quite distinct and common only to one or even just a few minerals. Many

collectors strive to collect mineral specimens of certain typical and abnormal habits (Fig. 1.11.).

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Fig. 1.11. Several types of crystal forms

Prismatic, columnar: crystals that commonly develop prism faces (Pict. 1.1.).

Acicular: crystals that grow in fine needles are (Pict. 1.2.).

Tabular, laminar: crystals growing flat plates (Pict. 1.3.).

Isometric: crystals growing in three dimension equally (Pict. 1.4.).

Pict. 1.1. Columnar crystal

– turmaline

Pict. 1.2. Acicular crystals

– antimonite

Pict. 1.3. Tabular crystals –

barite

Pict. 1.4. Isometric

crystals – granate

6. Twinning in Crystals

Parallel growth: Crystals that grow adjacent to each other may be aligned to resemble twinning. This simply

reduces system energy and is not twinning.

Oriented growth: it’s a special form of parallel growing, when younger crystal growths on the older one in the

same orientation.

Twinning: occurs when two separate crystals share some of the same crystal lattice points in a symmetrical

manner. The result is an intergrowth of two separate crystals in a variety of specific configurations.

Contact twins: have a planar composition surface separating 2 individual crystals. These are usually defined by a

twin law that expresses a twin plane (i.e. an added mirror plane). For example orthoclase has the Braveno Law,

or gypsum has the Swallow Tail Twins.

Penetration twins: have an irregular composition surface separating 2 individual crystals. These are defined by a

twin center or twin axis. For example the Carlsbad Law of orthoclase or the Staurolite Law of staurolite is very

common.

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Polysynthetic twins: if the compositions surfaces are parallel to one another. Plagioclase commonly shows this

type of twinning, called the Albite Twin Law. Such twinning is one of the most diagnostic features of

plagioclase. If the composition surfaces are not parallel to one another, they are called cyclical twins. Shown

here is the cyclical twin that occurs in chrysoberyl (Fig. 1.12.).

Fig. 1.12. The most common crystal twins

7. Physical characteristics of minerals

Colour: Colour in minerals is caused by the absorption, or lack of absorption, of various wavelengths of light.

The colour of light is determined by its wavelength. When pure white light (containing all wavelengths of

visible light) enters a crystal, some of the wavelengths might be absorbed while other wavelengths may be

emitted. If this happens then the light that leaves the crystal will no longer be white but will have some colour.

Elements that produce colours through absorption and emission of wavelengths are usually transition metals.

They can cause a mineral to always be a certain colour if they are part of the chemistry of the mineral. These are

the idiochromic minerals (Pict. 1.5.). However, if there is just a trace of these elements, they still can strongly

influence the colour of the mineral. These are the allochromic minerals (Pict. 1.6.). Even tiny amounts of these

elements can deeply collared minerals. It is erroneously thought that certain elements cause only certain colours

and there is some truth to that. Copper usually produces green and blue colours. Iron is known for the red and

yellow colours that it typically produces. However, almost any element can be responsible for any colour.

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Pict. 1.5. Idiochromic mineral – malachite

Pict. 1.6. Allochromic mineral – yellow quartz

Streak colour: Those minerals, although still subject to the effects of trace elements, always have the same basic

colour. Most minerals, however, are usually white or colourless in a pure state. Many impurities can colour

these minerals and make their colour variable. The property of streak often demonstrates the true or inherent

colour of a mineral. In addition to colouring elements, other impurities or factors exist that have also been linked

to the colour of minerals. Such things as elemental fluorine, sulphur, and chlorine; trace amounts of carbonate

and other ion groups; chlorine and fluorine ions and even structural defects. Radiation from rare earth minerals

can damage a crystal structure and this damage seems linked to colouring as in smoky quartz. Care should

always be given when trying to identify a mineral using colour.

Lustre: The way a mineral transmits or reflects light is a diagnostic property. This reflectance property is called

lustre. The most common types of lustre are:

Metallic: the look of metals. Opaque minerals are in this group, like native gold, native silver, native copper,

pyrite, chalcopyrite, galena, pyrolusite and chassiterite.

Submetallic: a poor metallic lustre. Minerals, which are opaque but their reflecting is little light, are in this

group, like native arsenic, graphite, liver ore, magnetite and ilmenite.

Adamantine: very gemmy crystals, like diamond, sphalerite, greenockite, cerussite, anglesite and zircone.

Vitreous: the most common lustre, it simply means the look of glass. Quartz, calcite, dolomite, malachite, barite,

gypsum, lazulite, beryl, granates and feldspars are in this group.

Pearly: the look of a pearl. It is characteristic at the perfect cleavage minerals, like gypsum, mica, brucite and

apophyllite.

Greasy and waxy: the look of grease or wax. There are some minerals in this group, like nepheline, oapl and

uraninite.

Silky: the look of silk, similar to fibrous but more compact. Clay minerals include to this group.

Special colours and lustres

Iridescence – Iridescence is generally known as the property of certain surfaces which appear to change colour

as the angle of view or the angle of illumination changes. It is common on the surface of opaque, metallic

minerals.

Shiller – It caused by small, laminar crystal inclusions (hematite, mica or lepidocrocite) inside the minerals.

Asterism – Asterism is a well-known light effect in some gemstones. The effect is caused by minute acicular

(needle-like) crystals of probably rutile or sometimes other minerals that are included in the host mineral. These

minute crystals are microscopic, but there are thousands of them and their combined effect is to diffract light

into these bands that appear as rays of light.

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Cat’s eye – Cat's eyes are similar to asterisms and are caused by the same inclusions of minute crystals. But in

this case the band on light is limited to one band that shimmers from the top to the bottom of the stone and

appears like a glowing cat's eye.

Opalescence – Opalescence is a type of dichroism seen in highly dispersed systems with little opacity. The

material appears yellowish-red in transmitted light and blue in the scattered light perpendicular to the

transmitted light. The phenomenon is named after the appearance of opals. It is a characteristic fenomena of

precious opal.

Labradorescence – It occurs in large crystal masses in anorthosite and shows a play of colors called

labradorescence. The labradorescence is the result of light refracting within lamellar intergrowths resulting from

phase exsolution (Pict. 1.7.).

Pict. 1.7. Labradorescence – labradorite

Adularescence – Adularescence is similar to labradorescence, produced most notably by moonstones. This

effect is most typically produced by adularia (also known as precious moonstone), from which the name derives,

but it appears in numerous other gemstones.

Hardness: is usually tested by seeing if some standard minerals are able to scratch others. A standard scale was

developed by Friedrich Mohs in 1812. The standard minerals making up the Mohs scale of hardness are:

The Mohs scale of hardness

Hardness Mineral mode of

determination

1 talc easy to

scratch by

nail

2 gypsum hard to

scratch by

nail

3 calcite easy to

scratch by

needle

4 fluorite easy to

scratch by

knife

5 apatite hard to

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scratch by

knife

6 orthoclase scratchable by

rasp

7 quartz these scratch

glass

8 topaz

9 corundum

10 diamond

Cleavage and fracture: Because bonding is not of equal strength in all directions in most crystals, they will tend

to break along crystallographic directions giving them a fracture property that reflects the underlying structure

and is frequently diagnostic. The tendency for minerals to cleave or not and in which directions is very

characteristic and therefore important to the identification of minerals. Cleavage is described in terms of how

easy the cleavage is produced. From easiest to hardest to produce the terms are: perfect, imperfect, good,

distinct, indistinct, and poor.

Fracture is a description of the way a mineral tends to break. Fracture occurs in all minerals even ones with

cleavage, although a lot of cleavage directions can diminish the appearance of fracture surfaces. Different

minerals will break in different ways and leave a surface that can be described in a recognizable way. The most

common fracture type is conchoidal. Quartz has this fracture type. Unlike uneven, jagged has sharp points or

edges that catch on a finger that's rubbed across the surface. Usually this indicates a metal such as copper , a

metal alloy or some sulfides or oxides. Earthy is a fracture that produces a texture similar to broken children's

clay. It is found in minerals that are generally massive and loosely consolidated such as limonite.

8. Inclusion in minerals

Many minerals have crystals of other minerals, air, water, tar, petroleum, rocks and in the case of amber even

animals included in their interiors. They are called, appropriately enough, inclusions (Pict. 1.8.).

Pict. 1.8. Opaque inclusions in fluorite

These inclusions are sometimes accidental such as when one crystal was growing and another mineral begins to

make a small crystal on the surface of the earlier mineral. The first mineral continues to grow and may grow

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over and around the second mineral, thereby enclosing it in its crystal. The second type of inclusion involves

minerals that formed after initial crystallization and is a result of exsolution. Some chemistries are favourable at

certain temperatures and pressures, but are unstable at different temperatures and pressures. The minerals will

then try and convert to a more stable chemistry and this often leads to the fractioning out of undesirable

chemistries, in different minerals. Rutile, TiO2, is a common inclusion mineral that forms in this way. Rutile

inclusions are responsible for the effects of asterism and chatoyancy. Some very rare minerals are only known

as small inclusions in other minerals. Inclusions of air and water are called two phase inclusions and are

commonly found in gypsum and quartz. Identification of inclusions is difficult because few property tests

(generally limited to colour, translucency, lustre and maybe crystal habit) can be performed on the including

crystal without removing it from the host mineral. Some optic tests can be performed however and a reliable

analysis can usually be obtained by a laboratory. Some invaluable and historic gemstones contain inclusions that

were identified in this way. Some inclusions turned out to be other gemstone minerals! At times inclusions can

be diagnostic and even assist in the identification of the minerals locality. Emeralds mined in Russia for

instance, are known to have tiny inclusions of actinolite, unlike other emeralds.

9. Pseudomorphs

A pseudomorph (which mean false shape in Latin) is a crystal that has replaced another mineral's chemistry or

structure with its own without changing the outward shape of the original mineral (Pict. 1.9.). Transformations

from one mineral to another are not unusual in nature, but preserving the outward shape of the original mineral

is! The end result is that the crystal appears to be one mineral but is actually another.

Pict. 1.9. Limonite showing pseudomorph after pyrite

10. Mineral occurrences and environments

In addition to physical properties, one of the most diagnostic features of a mineral is the geological environment

in which it is occurs. Learning to recognize different types of geological environments can be thus be very

helpful in recognizing the common minerals. For the purposes of aiding mineral identification, we have

developed a very rough classification of geological environments, most of which can be visited locally.

10.1. Igneous minerals

Minerals in igneous rocks must have high melting points and be able to co-exist with, or crystallize from,

silicate melts at temperatures above 800 º C. Igneous rocks can be generally classed according to their silica

content with low-silica (<< 50 % SiO2) igneous rocks being termed basic or mafic, and high-silica igneous

rocks being termed silicic or acidic. Basic igneous rocks (BIR) include basalts, dolerites, gabbros, kimberlites,

and peridotites, and abundant minerals in such rocks include olivine, pyroxenes, Ca-feldspar (plagioclase),

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amphiboles, and biotite. The abundance of Fe in these rocks causes them to be dark-coloured. Silicic igneous

rocks (SIR) include granites, granodiorites, and rhyolites, and abundant minerals include quartz, muscovite, and

alkali feldspars. These are commonly light-coloured although colour is not always diagnostic. In addition to

basic and silicic igneous rocks, a third igneous mineral environment representing the final stages of igneous

fractionation is called a pegmatite (PEG) which is typically very coarse-grained and similar in composition to

silicic igneous rocks (i.e. high in silica). Elements that do not readily substitute into the abundant minerals are

called incompatible elements, and these typically accumulate to form their own minerals in pegmatites. Minerals

containing the incompatible elements, Li, Be, B, P, Rb, Sr, Y, Nb, rare earths, Cs, and Ta are typical and

characteristic of pegmatites.

The fourth major mineral environment is hydrothermal, minerals precipitated from hot aqueous solutions

associated with emplacement of intrusive igneous rocks. This environment is commonly grouped with

metamorphic environments, but the minerals that form by this process and the elements that they contain are so

distinct from contact or regional metamorphic rocks that it us useful to consider them as a separate group. These

may be sub-classified as high temperature hydrothermal (HTH), low temperature hydrothermal (LTH), and

oxidized hydrothermal (OXH). Metals of the centre and right-hand side of the periodic table (e.g. Cu, Zn, Sb,

As, Pb, Sn, Cd, Hg, Ag) most commonly occur in sulphide minerals and are termed the chalcophile elements.

Sulphides may occur in igneous and metamorphic rocks, but are most typically hydrothermal. High temperature

hydrothermal minerals include gold, silver, tungstate minerals, chalcopyrite, bornite, the tellurides, and

molybdenite. Low temperature hydrothermal minerals include barite, gold, cinnabar, pyrite, and cassiterite.

Sulphide minerals are not stable in atmospheric oxygen and will weather by oxidation to form oxides, sulphates

and carbonates of the chalcophile metals, and these minerals are characteristic of oxidized hydrothermal

deposits. Such deposits are called gossans and are marked by yellow-red iron oxide stains on rock surfaces.

10.2. Sedimentary minerals

Minerals in sedimentary rocks are either stable in low-temperature hydrous environments (e.g. clays) or are high

temperature minerals that are extremely resistant to chemical weathering (e.g. quartz). One can think of

sedimentary minerals as exhibiting a range of solubilities so that the most insoluble minerals such as quartz

gold, and diamond accumulate in the coarsest detrital sedimentary rocks, less resistant minerals such as

feldspars, which weather to clays, accumulate in finer grained siltstones and mudstones, and the most soluble

minerals such as calcite and halite (rock-salt) are chemically precipitated in evaporite deposits. Accordingly, I

would classify sedimentary minerals into detrital sediments (DSD) and evaporites (EVP). Detrital sedimentary

minerals include quartz, gold, diamond, apatite and other phosphates, calcite, and clays. Evaporite sedimentary

minerals include calcite, gypsum, anhydrite, halite and sylvite, plus some of the borate minerals.

10.3. Metamorphic minerals

Minerals in metamorphic rocks have crystallized from other minerals rather than from melts and need not be

stable to such high temperatures as igneous minerals. In a very general way, metamorphic environments may be

classified as low-grade metamorphic (LGM) (temperatures of 60º to 400º C and pressures << .5 GPa (=15km

depth) and high-grade metamorphic (HGM) (temperatures > 400º and/or pressures > .5GPa). Minerals

characteristic of low- grade metamorphic environments include the zeolites, chlorites, and andalusite. Minerals

characteristic of high grade metamorphic environments include sillimanite, kyanite, staurolite, epidote, and

amphiboles.

Selected literatures

Bognár L. 1987: Ásványhatározó. – Gondolat Könyvkiadó, Budapest, p. 480.

Koch S. - Sztrókay K.I. 1967: Ásványtan I.–II. – Nemzeti Tankönyvkiadó, Budapest, p. 936.

Papp G. - Szakáll S. - Weiszburg T. (szerk.) 1993: Az erdıbényei Mulató-hegy ásványai. - Topographia

Mineralogica Hungariae. 1. Miskolc, Herman Ottó Múzeum, p. 89.

Papp G. - Szakáll S. (szerk.) (1997): Az Esztramos-hegy ásványai. - Topographia Mineralogica Hungariae, 5.

Miskolc, Herman Ottó Múzeum, p. 148.

Papp G. - Szakáll S. - Weiszburg T. - Fehér B. 1999: A dunabogdányi Csódi-hegy ásványai (Bevezetés). -

Topographia Mineralogica Hungariae, 1. Miskolc, Herman Ottó Múzeum 9-14.

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Szakáll S. (szerk.) 1996: 100 magyarországi ásványlelőhely. - Minerofil Kiskönyvtár II. Miskolc: Magyar

Minerofil Társaság, p. 139.

Szakáll S. 2007: A Tokaji-hegység ásványtani jellemzése. In (Baráz Cs., Kiss G. szerk.): A Zempléni

Tájvédelmi Körzet. Abaúj és Zemplén határán. Eger: Bükki Nemzeti Park. p. 45–54.

Szakáll S. 2007: Ásványrendszertan. 2., jav. kiadás. - Miskolci Egyetemi Kiadó, p. 336.

Szakáll S. 2008: Barangolás az ásványok világában. - Debrecen: Tóth Kiadó, p. 120

Szakáll S. - Gatter I. 1993: Magyarországi ásványfajok. Miskolc: Fair-System, p. 211.

Szakáll S. - Gatter I. - Szendrei G. 2005: A magyarországi ásványfajok. - Budapest, Kőország Kiadó, p. 427.

Szakáll S. - Jánosi M. 1995: Magyarország ásványai. - A Herman Ottó Múzeum állandó ásványtani kiállításának

vezetője. Miskolc, Herman Ottó Múzeum, p. 117.

Szakáll S. - Weiszburg T. (szerk.) 1994: A telkibányai érces terület ásványai. - Topographia Mineralogica

Hungariae, 2. Miskolc: Herman Ottó Múzeum, p. 258.

http://www.geomania.hu

http://webmineral.com

http://www.monstone.hu

http://www.minerals.hu

http://geology.com

BASICS OF PETROLOGY

Rock or stone is a naturally occurring solid aggregate of minerals and/or mineraloids. The Earth's outer solid

layer, the lithosphere, is made of rock. In general rocks are of three types, namely, igneous, sedimentary, and

metamorphic. The scientific study of rocks is called petrology, and petrology is an essential component of

geology.

Rocks are generally classified by mineral and chemical composition, by the texture of the constituent particles

and by the processes that formed them. These indicators separate rocks into igneous, sedimentary, and

metamorphic. They are further classified according to particle size. The transformation of one rock type to

another is described by the geological model called the rock cycle.

Igneous rocks are formed when molten magma cools and are divided into two main categories: plutonic rock

and volcanic. Plutonic or intrusive rocks result when magma cools and crystallizes slowly within the Earth's

crust (example granite), while volcanic or extrusive rocks result from magma reaching the surface either as lava

or fragmental ejecta (examples pumice and basalt). Sedimentary rocks are formed by deposition of either clastic

sediments, organic matter, or chemical precipitates (evaporites), followed by compaction of the particulate

matter and cementation during diagenesis. Sedimentary rocks form at or near the Earth's surface. Mud rocks

comprise 65% (mudstone, shale and siltstone); sandstones 20 to 25% and carbonate rocks 10 to 15% (limestone

and dolostone). Metamorphic rocks are formed by subjecting any rock type (including previously formed

metamorphic rock) to different temperature and pressure conditions than those in which the original rock was

formed. These temperatures and pressures are always higher than those at the Earth's surface and must be

sufficiently high so as to change the original minerals into other mineral types or else into other forms of the

same minerals (e.g. by recrystallisation).

The three classes of rocks — the igneous, the sedimentary and the metamorphic — are subdivided into many

groups. There are, however, no hard and fast boundaries between allied rocks. By increase or decrease in the

proportions of their constituent minerals they pass by every gradation into one another, the distinctive structures

also of one kind of rock may often be traced gradually merging into those of another. Hence the definitions

adopted in establishing rock nomenclature merely correspond to selected points (more or less arbitrary) in a

continuously graduated series.

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11. IGNEOUS ROCKS

Igneous rock is formed through the cooling and solidification of magma or lava. Igneous rock may form with or

without crystallization, either below the surface as intrusive (plutonic) rocks or on the surface as extrusive

(volcanic) rocks (Fig. 2.1.). This magma can be derived from partial melts of pre-existing rocks in either a

planet's mantle or crust. Typically, the melting is caused by one or more of three processes: an increase in

temperature, a decrease in pressure, or a change in composition. Over 700 types of igneous rocks have been

described, most of them having formed beneath the surface of Earth's crust. These have diverse properties,

depending on their composition and how they were formed.

Fig. 2.1. Types of intrusive and extrusive magma bodies

11.1. Classification

Igneous rocks are classified according to mode of occurrence, texture, mineralogy, chemical composition, and

the geometry of the igneous body.

The classification of the many types of different igneous rocks can provide us with important information about

the conditions under which they formed.

Two important variables used for the classification of igneous rocks are particle size, which largely depends

upon the cooling history, and the mineral composition of the rock. Feldspars, quartz or feldspathoids, olivines,

pyroxenes, amphiboles, and micas are all important minerals in the formation of almost all igneous rocks, and

they are basic to the classification of these rocks. All other minerals present are regarded as nonessential in

almost all igneous rocks and are called accessory minerals. Types of igneous rocks with other essential minerals

are very rare, and these rare rocks include those with essential carbonates.

In a simplified classification, igneous rock types are separated on the basis of the type of feldspar present, the

presence or absence of quartz, and in rocks with no feldspar or quartz, the type of iron or magnesium minerals

present. Rocks containing quartz (silica in composition) are silica-oversaturated. Rocks with feldspathoids are

silica-undersaturated, because feldspathoids cannot coexist in a stable association with quartz.

Igneous rocks which have crystals large enough to be seen by the naked eye are called phaneritic; those with

crystals too small to be seen are called aphanitic. Generally speaking, phaneritic implies an intrusive origin;

aphanitic an extrusive one.

An igneous rock with larger, clearly discernible crystals embedded in a finer-grained matrix is termed porphyry.

Porphyritic texture develops when some of the crystals grow to considerable size before the main mass of the

magma crystallizes as finer-grained, uniform material.

Texture is an important criterion for the naming of volcanic rocks. The texture of volcanic rocks, including the

size, shape, orientation, and distribution of mineral grains and the intergrain relationships, will determine

whether the rock is termed a tuff, a pyroclastic lava or a simple lava.

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However, the texture is only a subordinate part of classifying volcanic rocks, as most often there needs to be

chemical information gleaned from rocks with extremely fine-grained groundmass or from airfall tuffs, which

may be formed from volcanic ash.

Textural criteria are less critical in classifying intrusive rocks where the majority of minerals will be visible to

the naked eye or at least using a hand lens, magnifying glass or microscope. Plutonic rocks tend also to be less

texturally varied and less prone to gaining structural fabrics (Pict. 2.1.). Textural terms can be used to

differentiate different intrusive phases of large plutons, for instance porphyritic margins to large intrusive

bodies, porphyry stocks and subvolcanic dikes (apophyses) (Pict. 2.2.). Mineralogical classification is used most

often to classify plutonic rocks. Chemical classifications are preferred to classify volcanic rocks, with

phenocryst species used as a prefix, e.g. "olivine-bearing picrite" or "orthoclase-phyric rhyolite" (Pict. 2.3.).

Pict. 2.1. Crystalline

texture – granite

Pict. 2.2. Porphyritic

texture – andesite

Pict. 2.3. Aphanitic texture

- rhyolite

11.2. Basic classification scheme for igneous rocks on their mineralogy mineralogy

If the approximate volume fractions of minerals in the rock are known the rock name and silica content can be

read off the diagram. This is not an exact method because the classification of igneous rocks also depends on

other components than silica, yet in most cases it is a good first guess.

Igneous rocks can be classified according to chemical or mineralogical parameters:

11.3. Mineralogical classification

For volcanic rocks, mineralogy is important in classifying and naming lavas. The most important criterion is the

phenocryst species, followed by the groundmass mineralogy. Often, where the groundmass is aphanitic,

chemical classification must be used to properly identify a volcanic rock.

For intrusive, plutonic and usually phaneritic igneous rocks where all minerals are visible at least via

microscope, the mineralogy is used to classify the rock. This usually occurs on ternary diagrams, where the

relative proportions of four minerals (quartz, alkaline feldspars, plagioclases and feldspathoids) are used to

classify the rock. This system was worked out by Streckeisen (Fig. 2.2.).

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Fig. 2.2. Classification of igneous rocks using the QAPF diagram of Streckeisen

Felsic rock: highest content of silicon (SiO2> 70%), with predominance of quartz, alkali feldspars and

plagioclases: the felsic minerals; these rocks (e.g., granite, rhyolite) are usually light coloured, and have low

density.

Intermediate rock: silicon content is between 50-70%, with predominantly feldspars and plagioclases. Quartz

doesn’t occur in these rocks. They are usually dark coloured: grey, reddish or brownish (example andesite,

diorite).

Mafic rock: lesser content of silicon relative to felsic rocks (SiO2 < 50%), with predominance of mafic minerals

pyroxenes, olivines and calcic plagioclase; these rocks (example, basalt, gabbro) are usually dark coloured, and

have a higher density than felsic rocks.

Ultramafic rock: lowest content of silicon (SiO2 < 45%), with more than 90% of mafic minerals (e.g., dunite).

11.4. Chemical classification

Volcanic rocks can be classified on the base of total alkali-silica content (TAS diagram) when modal or

mineralogical data is unavailable:

ultrabasic igneous rocks with less than 44% silica (examples picrite and komatiite)

basic igneous rocks have low silica 44 - 53% and typically high iron - magnesium content (example gabbro and

basalt)

intermediate igneous rocks containing between 53 - 64% SiO2 (example andesite and dacite)

acid igneous rocks containing a high silica content, greater than 64% SiO2 (examples granite and rhyolite)

alkalic igneous rocks with 5 - 15% alkali (K2O + Na2O) content or with a molar ratio of alkali to silica greater

than 1:6 (examples phonolite and trachyte).

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(Note: the acid-basic terminology is used more broadly in older (generally British) geological literature. In

current literature felsic-mafic roughly substitutes for acid-basic.)

Chemical classification also extends to differentiating rocks which are chemically similar according to the TAS

diagram, for instance (Fig. 2.3.);

Ultrapotassic; rocks containing molar K2O/Na2O >3

Peralkaline; rocks containing molar (K2O + Na2O)/ Al2O3 >1

Peraluminous; rocks containing molar (K2O + Na2O)/ Al2O3 <1

An idealized mineralogy (the normative mineralogy) can be calculated from the chemical composition, and the

calculation is useful for rocks too fine-grained or too altered for identification of minerals that crystallized from

the melt. For instance, normative quartz classifies a rock as silica-oversaturated; an example is rhyolite. A

normative feldspathoid classifies a rock as silica-undersaturated; an example is nephelinite.

Fig. 2.3. Classification of pyroclastic rocks using the TAS diagram

11.5. Magma evolution

Most magmas only entirely melt for small parts of their histories. More typically, they are mixes of melt and

crystals, and sometimes also of gas bubbles. Melt, crystals, and bubbles usually have different densities, and so

they can separate as magmas evolve.

As magma cools, minerals typically crystallize from the melt at different temperatures (fractional

crystallization). As minerals crystallize, the composition of the residual melt typically changes. If crystals

separate from melt, then the residual melt will differ in composition from the parent magma. For instance, a

magma of gabbroic composition can produce a residual melt of granitic composition if early formed crystals are

separated from the magma. Gabbro may have a liquidus temperature near 1200°C, and derivative granite-

composition melt may have a liquidus temperature as low as about 700°C. Incompatible elements are

concentrated in the last residues of magma during fractional crystallization and in the first melts produced

during partial melting: either process can form the magma that crystallizes to pegmatite, a rock type commonly

enriched in incompatible elements. Bowen's reaction series is important for understanding the idealised

sequence of fractional crystallisation of a magma.

Magma composition can be determined by processes other than partial melting and fractional crystallization. For

instance, magmas commonly interact with rocks they intrude, both by melting those rocks and by reacting with

them. Magmas of different compositions can mix with one another. In rare cases, melts can separate into two

immiscible melts of contrasting compositions.

There are relatively few minerals that are important in the formation of common igneous rocks, because the

magma from which the minerals crystallize is rich in only certain elements: silicon, oxygen, aluminium, sodium,

potassium, calcium, iron, and magnesium. These are the elements which combine to form the silicate minerals,

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which account for over ninety percent of all igneous rocks. The chemistry of igneous rocks is expressed

differently for major and minor elements and for trace elements. Contents of major and minor elements are

conventionally expressed as weight percent oxides (e.g., 51% SiO2, and 1.50% TiO2). Abundances of trace

elements are conventionally expressed as parts per million by weight (e.g., 420 ppm Ni, and 5.1 ppm Sm). The

term "trace element" typically is used for elements present in most rocks at abundances less than 100 ppm or so,

but some trace elements may be present in some rocks at abundances exceeding 1000 ppm. The diversity of rock

compositions has been defined by a huge mass of analytical data—over 230,000 rock analyses can be accessed

on the web through a site sponsored by the U. S. National Science Foundation (see the External Link to

EarthChem).

11.6. The most important igneous rocks and their components

ULTRAMAFIC ROCKS

1, PERIDOTITE GROUP: Mains components are olivine> 40%, pyroxene, amphibole, (mica). Accessories are

metallic minerals, (ilmenite, magnetite, chrome iron), spinell, granate, apatite. Secondary components are

serpentine minerals, titanite, limonite. Rock types:

1.a, dunite: olivine> 90%

1.b, pyroxene peridotites:

- harzburgite: olivine> 40%, orthopyroxene

- lherzolite: olivine> 40%, clinopyroxene, orthopyroxene

- wehrlite: olivine> 40%, clinopyroxene

1.c, amphibole peridotite: olivine> 40%, amphibole

1.d, mica peridotite (kimberlite): olivine>40%, mica

1.e, metallic peridotite: olivine>40%, metallic minerals, (pyroxene, amphibole)

Extrusive rock types:

1.f, picrite: olivine, clinopyroxene

2, PYROXENITE GROUP: Main components are pyroxene>> olivine (<40%), amphibole. Accessories are

metallic minerals. Secondary components are serpentine minerals, chlorite. Rock types:

2.a, pyroxenite: pyroxene, olivine<40%

2.b, clinopyroxenite: clinopyroxene

2.c, orthopyroxenite: orthopyroxene

2.d, websterite: clinopyroxene, orthopyroxene

3, HORNBLENDITE GROUP: Main components are amphibole (mainly hornblende)>> pyroxene, olivine.

Accessories are metallic minerals. Secondary components are chlorite. Rock type:

3.a, hornblendite: hornblende, (olivine<40%, pyroxene)

MAFIC ROCKS

1, GABBRO GROUP: Main components are basic plagioclase, pyroxene, olivine, amphibole. Accessories are

apatite, magnetite, ilmenite. Secondary components are chlorite, titanite, serpentine minerals, epidote. Rock

types:

intrusive:

1.a, gabbro: basic plagioclase, pyroxene (amphibole)

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1.b, olivine gabbro: basic plagioclase, olivine, pyroxene (amphibole)

1.c, norite: basic plagioclase, orthopyroxene

1.d, troctolite: basic plagioclase, olivine

1.e, anortosite: basic or neutral plagioclase>90%

extrusive:

2.a, basalt: basic plagioclase, pyroxene (amphibole)

2.b, olivine basalt: basic plagioclase, olivine, pyroxene (amphibole)

subvolcanic and dyke types:

3.a, dolerite: basic plagioclase, pyroxene (olivine, amphibole)

3.b, diabase: old name of partly altered, greenish metabasalt or metadolerite

NEUTRAL ROCKS

1, DIORITE GROUP: Main components are neutral plagioclase, amphibole, biotite, pyroxene, ((K-feldspar)).

Accessories are apatite, magnetite, granate. Secondary components are chlorite, sericite, epidote. Rock types:

intrusive:

1.a, diorite: neutral plagioclase, amphibole, biotite, pyroxene (if a mafic component is dominant, the name of the

rock: amphibole diorite, pyroxene diorite, mica diorite)

extrusive:

1.b, andesite: neutral plagioclase, amphibole, biotite, pyroxene; if a mafic component is dominant, the name of

the rock: amphibole andesite, pyroxene andesite, biotite-amphibole andesite.

2. MONZONITE GROUP: Main components are neutral plagioclase ≈ K-feldspar, amphibole, pyroxene, biotite.

Accessories are apatite, magnetite, zircon. Secondary components are chlorite, sericite, epidote. Rock types:

intrusive:

2.a, monzonite: neutral plagioclase ≈ orthoclase- microcline, amphibole, pyroxene, biotite

extrusive:

2.b, latite: neutral plagioclase ≈ sanidine, amphibole, pyroxene, biotite

3. SYENITE GROUP: Main components are K-feldspar>> neutral plagioclase, amphibole, pyroxene, biotite.

Accessories are titanite, zircon, apatite, magnetite. Secondary components are clorite, sericite. Rock types:

intrusive:

3.a, syenite: K-feldspar (orthoclase- microcline) >>neutral plagioclase, amphibole, pyroxene, biotite

extrusive:

3.b, trachite: sanidine>>neutral plagioclase, amphibole, pyroxene, biotite

FELSIC ROCKS

1, GRANODIORITE GROUP: Main components are felsic plagioclase> K-feldspar, quartz, biotite, amphibole.

Accessories are zircon, apatite, magnetite. Secondary components are sericite, chlorite, epidote. Rock types:

intrusive:

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1.a, granodiorite: felsic plagioclase >orthoclase- microcline, quartz, biotite, amphibole

1.b, tonalite: felsic plagioclase, quartz, amphibole, biotite

extrusive:

1.c, dacite: felsic plagioclase >>sanidine, quartz, biotite, amphibole, (orthopyroxene)

2, GRANITE GROUP: Main components are K-feldspar> felsic plagioclase, quartz, biotite, amphibole.

Accessories are zircon, apatite, turmaline, magnetite. Secondary components are sericite, epidote, chlorite. Rock

types:

intrusive:

2.a, granite: orthoclase- microcline> felsic plagioclase, quartz, biotite, amphibole

varieties: runite – oriented growth of quartz and orthoclase

luxullianite – (turmaline granite) – is has high turmaline content as accessories

extrusive:

2.b, rhyolite: sanidine> felsic plagioclase, quartz, biotite

vitreous varieties: obsidian (water content: 1-2%) – black colour, conchoidal fracture, glassy lustre

pitchstone (water content: 6-9%) – pitch lustre, uneven fracture

perlite (water content 3-5%) – it’s built by spheroidal "pearls"

pumice – porous rock with vesicles; unit weight is small

vesicular rhyolite – it contains semi-parallel vesicles with thick wall

spherulitic rhyolite – it evolves by recrystallisation

dyke type:

2.c, aplite: orthoclase- microcline> felsic plagioclase, quartz, (biotite, amphibole); microcrystalline, quantity of

mafic components are very low.

12. SEDIMENTARY ROCKS

Sedimentary rock is a type of rock that is formed by sedimentation of material at the Earth's surface and within

bodies of water. Sedimentation is the collective name for processes that cause mineral and/or organic particles

(detritus) to settle and accumulate or minerals to precipitate from a solution. Particles that form a sedimentary

rock by accumulating are called sediment. Before being deposited, sediment was formed by weathering and

erosion in a source area, and then transported to the place of deposition by water, wind, mass movement or

glaciers which are called agents of denudation.

The sedimentary rock cover of the continents of the Earth's crust is extensive, but the total contribution of

sedimentary rocks is estimated to be only 5% of the total volume of the crust. Sedimentary rocks are only a thin

veneer over a crust consisting mainly of igneous and metamorphic rock.

Sedimentary rocks are deposited in layers as strata, forming a structure called bedding. The study of

sedimentary rocks and rock strata provides information about the subsurface that is useful for civil engineering,

for example in the construction of roads, houses, tunnels, canals or other constructions. Sedimentary rocks are

also important sources of natural resources like coal, fossil fuels, drinking water or ores.

The study of the sequence of sedimentary rock strata is the main source for scientific knowledge about the

Earth's history, including palaeogeography, paleoclimatology and the history of life.

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The scientific discipline that studies the properties and origin of sedimentary rocks is called sedimentology.

Sedimentology is both part of geology and physical geography and overlaps partly with other disciplines in the

Earth sciences, such as pedology, geomorphology, geochemistry or structural geology.

Based on the processes responsible for their formation, sedimentary rocks can be subdivided into four groups:

clastic sedimentary rocks, biochemical (or biogenic) sedimentary rocks, chemical sedimentary rocks and a

fourth category for "other" sedimentary rocks formed by impacts, volcanism, and other minor processes.

12.1. Clastic sedimentary rocks

Clastic sedimentary rocks are composed of silicate minerals and rock fragments that were transported by

moving fluids (as bed load, suspended load, or by sediment gravity flows) and were deposited when these fluids

came to rest. Clastic rocks are composed largely of quartz, feldspar, rock (lithic) fragments, clay minerals, and

mica; numerous other minerals may be present as accessories and may be important locally.

Clastic sediment, and thus clastic sedimentary rocks, are subdivided according to the dominant particle size

(diameter). Most geologists use the Udden-Wentworth grain size scale and divide unconsolidated sediment into

four fractions: gravel (>2 mm diameter); sand (1/16 to 2 mm diameter); mud (clay is <1/256 mm; silt (is

between 1/16 and 1/256 mm) (Table 2.1.).

Grain size (mm) incoherent debris cemented

rocks

>256 boulder coarse

grained

rocks:

conglomerate

breccia

64-256 coarse grain gravel

4-64 gravel

2-4 fine grain gravel

1-2 coarse grained sand sandstone

0,5-1 semi-coarse grained sand

0,25-0,5 medium-grained sand

0,125-0,25 small-grained sand

0,063-0,125 fine grained sand

0,031-0,063 coarse grained aleurite aleurolite "mudrock"

0,016-0,031 medium-grained aleurite

0,008-0,016 fine grained aleurite

0,004-0,008 very fine grained aleurite

<0,004 clay clay stone

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Table 2.1. Classification of siliciclastic rocks on the base of their grain size (Szakmány 2008)

The classification of clastic sedimentary rocks parallels this scheme; conglomerates and breccias are made

mostly of gravel, sandstones are made mostly of sand, and mudrocks are made mostly of mud. This tripartite

subdivision is mirrored by the broad categories of rudites, arenites, and lutites, respectively, in older literature.

Subdivision of these three broad categories is based on differences in clast shape (conglomerates and breccias),

composition (sandstones), grain size and/or texture (mudrocks).

Sedimentary rocks content different sized grains offer. When the rock is built by two or more dominant grain

size it is necessary to sign it in the name of the rock (example sandy marl) (Fig. 2.4.).

Fig. 2.4. Classification of clastic sedimentary rocks

Components of siliciclastic rocks

Components of the siliciclastic rocks can be separated to four groups: 1, grains; 2, matrix; 3, cement; 4, pores

(Fig. 2.5.). Grains and the fine matrix are primer components while cement and some coarse matric arise during

the process of diagenesis. The pores can be primer and secondary components also.

There are two important properties of grans which people use to determinete siliciclastic rocks. These are the

roundness (Fig. 2.6.) and sorting (Fig. 2.7.).

Fig. 2.5. Dominant components of clastic sedimentary rocks

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Fig. 2.6. Types of roundness of the grains in clastic sedimentary rocks

Fig. 2.7. Types of grain sorting of clastic sedimentary rocks

12.1.1. Conglomerates and breccias

The dominant grain size is >2 mm. Conglomerates are dominantly composed of rounded gravel and breccias are

composed of dominantly angular gravel.

Classification

a, Grain size, roundness, cementing

Grain shape Incoherent Cemented Grain size

angular

rounded

Block

Boulder

-

-

> 20 cm

angular

rounded

Coarse grained debris

Coarse grained gravel

Coarse grained breccia

Coarse grained

conglomerate

20-2 cm

angular

rounded

Fine grained debris

Fine grained gravel

Fine grained breccia

Fine grained conglomerate

2-0,5 cm

angular

rounded

Rock sleet

Very fine grained gravel

Fine grained breccia

Fine grained conglomerate

0,5-0,2 cm

Table 2.2. Classification of coarse grained siliciclastic rocks on the base of an older Hungarian system (after

Bárdossy, 1961)

b, Material of grains

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Monomict: more than 90 percentage of the grains has a same material.

Oligominct: 50-90 percentage of the grains has a same material.

Polymict: less than 50 percentage of the grains has a same material.

c, Texture

Orthoconglomerate: the quantity of the matrix is less than 15 percentage; bimodal grain-size distribution; grain-

supported.

Paraconglomerate: the quantity of the matrix is more than 15 percentage; poorly sorted, polymodal grain-size

distribution; matrix-supported.

d, Genesis

Intraformational conglomerate: grains origine from inside of the basin

Extraformational conglomerate: grains origine from outside of the basin

12.1.2. Sandstones

The relative abundance of sand-sized framework grains determines the first word in a sandstone name. For

naming purposes, the abundance of framework grains is normalized to quartz, feldspar, and lithic fragments

formed from other rocks. These are the three most abundant components of sandstones; all other minerals are

considered accessories and not used in the naming of the rock, regardless of abundance.

Classification

a, Grain size, cementing

Incoherent Cemented Grain size

Coarse grained sand Coarse grained sandstone 2-0,5 mm

Medium-grained sand Medium grained sandstone 0,5-0,2 mm

Small-grained sand Small-grained sandstone 0,2-0,1 mm

Fine grained sand Fine grained sandstone 0,1-0,06 mm

Table 2.3. Classification of sands and sandstones on the base of an older Hungarian system (after Bárdossy,

1961)

b, Material of grains

Monomict: more than 90 percentages of the grains have a same material.

Oligominct: 50-90 percentages of the grains have a same material.

Polymict: less than 50 percentages of the grains have a same material.

Maturity of sandstones (Fig. 2.8.):

Immaturate: clay-content is more than 5 percentages; poorly sorted; grains are angular

Poorly maturate: clay-content is less than 5 percentages; poorly sorted; grains are angular

Maturate: no clay-content, well sorted; grains are angular

Very maturate: no clay-content, well sorted; grains are well rounded

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Fig. 2.8. Types of maturity of sandstones

Six sandstone names are possible using descriptors for grain composition (quartz-, feldspathic-, and lithic-) and

amount of matrix (wacke or arenite). For example, a quartz arenite would be composed of mostly (>90%) quartz

grains and have little/no clayey matrix between the grains, a lithic wacke would have abundant lithic grains

(<90% quartz, remainder would have more lithics than feldspar) and abundant muddy matrix, etc.

12.1.3. Fine-grained sedimentary rocks

Grain size of these rocks is smaller than 0,06 mm. Several aleurolites and clays contains into this group.

Classification

a, Grain size, cementing

Incoherent Cemented Grain

size

Coarse grained silt/aleurite Aleurolite 0,06-0,02

mm

Fine grained silt/aleurite 0,02-0,005 mm

Table 2.4. Classification of fine-grained sedimentary rocks on the base of an older Hungarian system (after

Bárdossy, 1961)

Loess: Loess is aeolian sediment formed by the accumulation of wind-blown silt, typically in the 0.02-0.06 mm

size range. It composed of crystals of quartz, feldspar, mica and other minerals. Grains are loosely cemented by

calcium carbonate. It is usually homogeneous and highly porous and is traversed by vertical capillaries that

permit the sediment to fracture and form vertical bluffs. Loess doll: Loess deposits sometimes contain "pebbles"

called or "loess dolls". These nodules of calcium carbonate range in size from peas to baseballs or grapefruit.

They were formed by infiltrating precipitation that dissolved and leached carbonate grains in the loess. As water

moved downward, the lime was redeposited around some nucleus to form the unusually shaped concretions.

12.1.4. Mudrocks

Mudrocks are sedimentary rocks composed of at least 50% silt- and clay-sized particles. These relatively fine-

grained particles are commonly transported as suspended particles by turbulent flow in water or air, and

deposited as the flow calms and the particles settle out of suspension.

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Most authors presently use the term "mudrock" to refer to all rocks composed dominantly of mud. Mudrocks

can be divided into siltstones (composed dominantly of silt-sized particles), mudstones (subequal mixture of

silt- and clay-sized particles), and claystones (composed mostly of clay-sized particles). Most authors use

"shale" is a term for a fissile mudrock (regardless of grain size), although some older literature uses the term

"shale" as a synonym for mudrock.

Classification

Mudrocks are classified on the base of their components.

1, Siallite: It contains clay minerals mostly. The name of these rocks is determined by their components, like

caolinitic clay, bentonite.

2, Allite: The dominant minerals are the Al-hydroxides and Al-oxy-hydroxides (gibbsite, diaspora, böhmite).

These rocks are the so called bauxites.

Classification of these rocks happened on the base of the rate of Al2O3/SiO2 minerals (Table 2.5.).

Al2O3/SiO2 allite-containing

Bauxitic clay 0,86 – 1,14 0-25 %

Clayey bauxite 1,14 – 3,4 25-75 %

Bauxit 3,4 felett >75 %

Table 2.5. Transitory rocks of siallites and allites (Szakmány 2008)

12.2. Carbonate rocks

Carbonate rocks are made of particles (composed >50% carbonate minerals) embedded in a cement. Most

carbonate rocks result from the accumulation of bioclasts created by calcareous organisms. Therefore carbonate

rocks originate in area favouring biological activity i.e. in shallow and warm seas in areas with little to no

siliciclastic input. In present day Earth these areas are limited to ±40 latitude in region away or protected from

erosion-prone elevated continental areas.

12.2.1. Components of the limestones

The sedimentologists divide the components of carbonates into two groups after Folk.

a, Orthochemical components: are those in which the carbonate crystallized in place.

Micrite: The micrite results from recrystallization of carbonate mud during diagenesis or from direct

precipitation of calcite, and causes lithifaction of the sediment. The size of grains is smaller than 4 μm.

Sparite: Larger sparry calcite matrix results from diagenesis in the same way that calcite cement originates in

sandstones. The size of grains is bigger than 15 μm.

Microsparite: Small sized sparite. It evolves at the beginning of the micrite’s recrystallization. The size of grains

is 4-15 μm.

b, Allochemical components: are those that contain grains brought in from elsewhere (i.e. similar to detrital

grains in clastic rocks).

Intraclasts: These are fragments of earlier formed limestone originated within the basin of deposition.

Peloids: These are spherical aggregates of microcrystalline calcite of coarse silt to fine sand size. Most appear to

be fecal pellets from burrowing benthic organisms. The size of these peloids are 0,1-2,0 mm.

Pellets: These are rounded aggregates of microcrystalline calcite. The size of these are 0,02-2,0 mm.

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Aggregates: These are rounded components, which consist two or more cemented grains.

Fossiliferous material: Whole or broken skeletons of organisms. 0,02-2,0 mm. They are coprolites in their

origin.

Ooids: These are spherical sand sized particles that have a concentric or radial internal structure. The central

part of each particle consists of a grain of quartz or other carbonate particle surrounded by thin concentric layers

of chemically precipitated calcite.

Pizoids: They are similar to the ooids but their size are bigger.

Oncoids: These are irregular, concentric component with two or more nuclei. Their size are bigger than 2 mm.

There are so called extraclast also, which origined from other rocks.

12.2.2. Classification

Two classification schemes are in common use by those who work on carbonate rocks. Although you will use

only the Folk classification in lab, you should also become familiar with the Dunham classification since it is

widely used as well.

Folk classification

The Folk classification use the type of components to classify limestones. Allochemical rocks are those that

contain grains brought in from elsewhere (i.e. similar to detrital grains in clastic rocks). Orthochemical rocks are

those in which the carbonate crystallized in place. Allochemical rocks have grains that may consist of

fossiliferous material, ooids, peloids, or intraclasts. These are embedded in a matrix consisting of

microcrystalline carbonate (calcite or dolomite), called micrite, or larger visible crystals of carbonate, called

sparite. Sparite is clear granular carbonate that has formed through recrystallization of micrite, or by

crystallization within previously existing void spaces during diagenesis.

The name of the rock contains the type of the orthochemical and allochemical components (example oosparite,

biomicrite) (Table 2.6.).

Quantity of allochemical components >10%

allochemical

component

<10%

allochemical

component

Rocks of

reefs and

biohermas

sparite>micrit

e micrite>sparit

e 1-10% allochemical component <1% allo-

chemical

component

>25% intraclast intrasparite intramicrite dominant

allochemical

components

intraclasts

micrite

with

intraclast

content

micrite or

dismicrite

(if it

contains

sparite)

<25%

intraclast >25% ooid oosparite oomicrite

ooids

micrite with

ooid content

<25% ooid >3:1 biosparite biomicrite

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bioclasts

micrite with

fossil content

between 3:1

and 1:3 biopelsparite biopelmicrite

biolithit

peloids

micrite with

peloid content

<1:3 pelsparite pelmicrite

Table 2.6. Classification of limestones after Folk (1959, 1962)

Dunham classification

The Dunham classification is based on the concept of grain support. The classification divides carbonate rocks

into two broad groups, those whose original components were not bound together during deposition and those

whose original components formed in place and consist of intergrowths of skeletal material. The latter group are

called boundstones (similar to biolithite of the Folk classification). The former group is further subdivided as to

whether or not the grains are mud-supported or grain supported. If the rock consists of less than 10% grains it is

called a mudstone (potentially confusing if taken out of context). If it is mud supported with greater than 10%

grains it is called a wackstone. If the rock is grain supported, it is called a packstone, if the grains have shapes

that allow for small amounts of mud to occur in the interstices, and a grainstone if there is no mud between the

grains (Table 2.7.).

Original components not bound

together during deposition Original components bound together

during the deposition

contains mud (particles of clay and

fine silt size) lacks mud

mud-supported grain-supported

less than 10% allockemical

components more than 10% allochemical

components

mudstone wackestone packstone grainstone boundstone

Table 2.7. Classification of limestones after Dunham (1962)

12.2.3. Terrestrial limestones

Carbonate rocks can be evolving in terrestrial environments also like caves, lakes and springs. Terrestrial

carbonates are for example:

Dropstone: Characteristic formation of karst caves. Carbonate-rich water leaves their carbonate content on the

roof of the cave because of the low pressure. Dropstone which is hanging to the roof called stalagmite. While if

it grows on the floor called stalactite.

Travertine: Carbonate deposition can occur in non-marine lakes as a result of evaporation. This is a massive,

thick layered rock. But travertine occurs at carbonate-rich springs also. When water saturated with calcium

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carbonate reaches the surface of the Earth at the spring, the water evaporates and cools resulting in the

precipitation of calcite to form of limestone. This is a porous, light rock.

12.2.4. Other calciferous rocks

Chalk: It is a soft, white, porous sedimentary rock, a form of limestone composed of the mineral calcite. Calcite

is calcium carbonate or CaCO3. It forms under reasonably deep marine conditions from the gradual

accumulation of minute calcite plates (coccoliths) and foraminiferas.

Dolomite: It is a carbonate mineral composed of calcium magnesium carbonate CaMg(CO3)2. The term is also

used to describe the sedimentary carbonate rock dolostone. Dolostone (dolomite rock) is composed

predominantly of the mineral dolomite with a stoichiometric ratio of 50% or greater content of magnesium

replacing calcium, often as a result of diagenesis.

12.3. Mixed rocks

Marl: It is a calcium carbonate rich mud or mudstone which contains variable amounts of clays and aragonite.

Marl was originally an old term loosely applied to a variety of materials, most of which occur as loose, earthy

deposits consisting chiefly of an intimate mixture of clay and calcium carbonate, formed under freshwater

conditions; specifically an earthy substance containing 35-65% clay and 65-35% carbonate.

12.4. "Other" sedimentary rocks

Iron-rich sedimentary rocks are composed of >15% iron; the most common forms are banded iron formations

and ironstones. Iron-rich sedimentary rocks can be oxide ironstones (oolitic ironstone, bog iron, banded

ironstone) or carbonate ironstones (white iron ore, black iron ore).

Siliceous sedimentary rocks are almost entirely composed of silica (SiO2), typically as chert, opal, chalcedony

or other microcrystalline forms. Chert is a mineralogically simple rock consisting of microcrystalline quartz.

Deposits of chert formed from the accumulation of siliceous skeletons from microscopic organisms such as

radiolaria and diatoms.

Manganeous sedimentary rocks are composed of > 8% Mn-minerals. Those can be carbonate Mn-rocks and

oxide Mn-rocks.

Phosphatic sedimentary rocks are composed of phosphate minerals and contain more than 6.5% phosphorus;

examples include deposits of phosphate nodules, bone beds, and phosphatic mudrocks..

Evaporite sedimentary rocks are composed of minerals formed from the evaporation of water. Evaporite

minerals are those minerals produced by extensive or total evaporation of a saline solution. The most common

evaporite minerals are carbonates (calcite and others based on CO32−), chlorides (halite and others built on

Cl−), and sulfates (gypsum and others built on SO42−). Evaporite rocks commonly include abundant halite

(rock salt), gypsum, and anhydrite.

Organic-rich sedimentary rocks have significant amounts of organic material, generally in excess of 5% total

organic carbon. Common examples include coal, oil shale, and other sedimentary rocks that act as reservoirs for

liquid hydrocarbons and natural gas. Coal which forms as plants remove carbon from the atmosphere and

combine with other elements to build their tissue.

12.5. Volcanoclastites

Volcanoclastites or pyroclastites are sedimentary rocks gearing to explosive volcanism. It contains more than

75% primer volcanic clasts. Components of volcanoclastic rocks are the following:

- Juvenile components: vesicular magmatic components. These evolve during the fragmentation of magma.

- Crystals: Whole or fragmented crystals, which crystallized in the magma chamber.

- Lithic components: Rock fragments with massive inner structure.

12.5.1. Classification of pyroclastites on the base of grain size

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Pyroclastites can be classified on the base of their grain size when they content more than 75% volcanic clasts

(Table 2.8.).

grain size incoherent sediment diagenized

rock

> 64 mm block (angular) pyroclastic

breccia

bomb (rounded) pyroclastic agglomerate

2 - 64 mm lapilli lapillite

0,0625 – 2 mm coarse grained ash coarse

grained

tuff

< 0,0625 mm fine grained ash fine

grained tuf

Table 2.8. Classification of pyroclastites (Szakmány 2008)

We can determine pyroclastic rocks on the base of their chemism also (for example rhyolite tuff, andesite tuff,

basalt tuff).

12.5.2. Arise of pyroclastites

Characteristics of eruption:

When magmas reach the surface of the Earth they erupt from a vent. They may erupt explosive or

phreatomagmatic.

- Explosive volcanism: Explosive eruptions are favored by high gas content and high viscosity. Explosive

bursting of bubbles will fragment the magma into clots of liquid that will cool as they fall through the air.

- Phreatomagmatic volcanism: These eruptions are produced when magma comes in contact with shallow

groundwater causing the groundwater to flash to steam and be ejected along with pre-existing fragments of the

rock and tephra from the magma. Because the water expands so rapidly, these eruptions are violently explosive

although the distribution of pyroclasts around the vent is much less than in a Plinian eruption. Phreatic eruptions

is a type of this. The magma encounters shallow groundwater, flashing the groundwater to steam, which is

explosively ejected along with pre-exiting fragments of rock. No new magma reaches the surface.

Type of the eruption’s process:

Ash falls: When a volcano erupts, it will eject a wide variety of material into the air above it (called pyroclastic

fall). The fine material (millimetre-sized ash), which is derived from volcanic glass, rock and crystal particles,

can be carried by currents in the eruption column to high above the volcano and pass into the downwind plume

to rain out forming ash fall deposits.

Pyroclastic flows: If a large volume of volcanic debris is erupted quickly from a volcano, the eruption column

can collapse, like pointing a garden hose directly up in the sky. As the eruption column collapses it can

transform into an outwardly expanding flood of hot solid ejecta in a fluidizing gas cloud. This is known as a

pyroclastic flow. The flow direction may be topographically controlled. Flows often travel at speeds up to 200

km/h, and cause total destruction of the areas they cover. Flows maybe very hot (several hundred oC) and can

start fires. Some pyroclastic surges are cooler (usually less than 300oC) and often deposit sticky wet mud.

12.5.3. Pyroclastic surges:

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Pyroclastic surges are low density flows of pyroclastic material. The reason they are low density is because they

lack a high concentration of particles and contain a lot of gases. These flows are very turbulent and fast. They

overtop high topographic features and are not confined to valleys. However, this type of flow usually does not

travel as far as a pyroclastic flow. Pyroclastic surges can travel up to at least 10 kilometers from the source.

There are three types of pyroclastic surges: 1) base surge, 2) ash cloud surge, and 3) ground surge. A base surge

is usually formed when the volcano initially starts to erupt from the base of the eruption column as it collapses.

It usually does not travel greater than 10 kilometers from its source. A ground surge usually forms at the base of

a pyroclastic flow. An ash cloud surge forms when the eruption column is neither buoying material upward by

convection or collapsing.

Types of volcanic eruptions:

Volcanic eruptions, especially explosive ones, are very dynamic phenomena. That is the behavior of the

eruption is continually changing throughout the course of the eruption. This makes it very difficult to classify

volcanic eruptions. Nevertheless they can be classified according to the principal types of behavior that they

exhibit. An important point to remember, however, is that during a given eruption the type of eruption may

change between several different types.

Hawaiian - These are eruptions of low viscosity basaltic magma. Gas discharge produces a fire fountain that

shoots incandescent lava up to 1 km above the vent. The lava, still molten when it returns to the surface flows

away down slope as a lava flow. Hawaiian Eruptions are considered non-explosive eruptions. Very little

pyroclastic material is produced.

Strombolian - These eruptions are characterized by distinct blasts of basaltic to andesitic magma from the vent.

These blasts produce incandescent bombs that fall near the vent, eventually building a small cone of tephra

(cinder cone). Sometimes lava flows erupt from vents low on the flanks of the small cones. Strombolian

eruptions are considered mildly explosive, and produce low elevation eruption columns and tephra fall deposits.

Plinian - These eruptions result from a sustained ejection of andesitic to rhyolitic magma into eruption columns

that may extend up to 45 km above the vent. Eruption columns produce wide-spread fall deposits with thickness

decreasing away from the vent, and may exhibit eruption column collapse to produce pyroclastic flows. Plinian

ash clouds can circle the Earth in a matter of days. Plinian eruptions are considered violently explosive.

Vulcanian - These eruptions are characterized by sustained explosions of solidified or highly viscous andesite or

rhyolite magma from a the vent. Eruption columns can reach several km above the vent, and often collapse to

produce pyroclastic flows. Widespread tephra falls are common. Vulcanian eruptions are considered very

explosive.

Pelean - These eruptions result from the collapse of an andesitic or rhyolitic lava dome, with or without a

directed blast, to produce glowing avalanches or nuée ardentes, as a type of pyroclastic flow known as a block-

and-ash flow. Pelean eruptions are considered violently explosive.

13. METAMORPHIC ROCKS

Metamorphic rock is the transformation of an existing rock type, the protolith, in a process called

metamorphism, which means "change in form". The protolith is subjected to heat and pressure (temperatures

greater than 150 to 200 °C and pressures of 1500 bars) causing profound physical and/or chemical change. The

protolith may be sedimentary rock, igneous rock or another older metamorphic rock. Metamorphic rocks make

up a large part of the Earth's crust and are classified by texture and by chemical and mineral assemblage

(metamorphic facies). They may be formed simply by being deep beneath the Earth's surface, subjected to high

temperatures and the great pressure of the rock layers above it. They can form from tectonic processes such as

continental collisions, which cause horizontal pressure, friction and distortion. They are also formed when rock

is heated up by the intrusion of hot molten rock called magma from the Earth's interior. The study of

metamorphic rocks (now exposed at the Earth's surface following erosion and uplift) provides information about

the temperatures and pressures that occur at great depths within the Earth's crust (Fig. 2.9.). Some examples of

metamorphic rocks are gneiss, slate, marble, schist, and quartzite.

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Fig. 2.9. Metamorphism in the case of pressure and temperature alternation

13.1. Limits of metamorphism

The temperature lower limit of metamorphism is considered to be 100 - 200°C, to exclude diagenetic changes,

due to compaction, which result in sedimentary rocks. There is no agreement on a pressure lower limit. Some

workers argue that changes in atmospheric pressures are not metamorphic, but some types of metamorphism can

occur at extremely low pressures.

The upper boundary of metamorphic conditions is related to the onset of melting processes in the rock. The

maximum temperature for metamorphism is typically 700 - 900°C, depending on the pressure and on the

composition of the rock. Migmatites are rocks formed at this upper limit, which contain pods and veins of

material that has started to melt but has not fully segregated from the refractory residue. Since the 1980s it has

been recognized that, rarely, rocks are dry enough and of a refractory enough composition to record without

melting "ultra-high" metamorphic temperatures of 900 - 1100°C.

13.2. Metamorphic rocks and index minerals

Metamorphic minerals are those that form only at the high temperatures and pressures associated with the

process of metamorphism. These minerals, known as index minerals, include sillimanite, kyanite, staurolite,

andalusite, and some garnet.

Other minerals, such as olivines, pyroxenes, amphiboles, micas, feldspars, and quartz, may be found in

metamorphic rocks, but are not necessarily the result of the process of metamorphism. These minerals formed

during the crystallization of igneous rocks. They are stable at high temperatures and pressures and may remain

chemically unchanged during the metamorphic process. However, all minerals are stable only within certain

limits, and the presence of some minerals in metamorphic rocks indicates the approximate temperatures and

pressures at which they formed.

The change in the particle size of the rock during the process of metamorphism is called recrystallization. For

instance, the small calcite crystals in the sedimentary rock limestone change into larger crystals in the

metamorphic rock marble, or in metamorphosed sandstone, recrystallization of the original quartz sand grains

results in very compact quartzite, in which the often larger quartz crystals are interlocked. Both high

temperatures and pressures contribute to recrystallization. High temperatures allow the atoms and ions in solid

crystals to migrate, thus reorganizing the crystals, while high pressures cause solution of the crystals within the

rock at their point of contact.

13.3. Some mechanism of methamorpism

13.3.1. Foliation

The layering within metamorphic rocks is called foliation (derived from the Latin word folia, meaning "leaves"),

and it occurs when a rock is being shortened along one axis during recrystallization. This causes the platy or

elongated crystals of minerals, such as mica and chlorite, to become rotated such that their long axes are

perpendicular to the orientation of shortening. This results in a banded, or foliated, rock, with the bands showing

the colours of the minerals that formed them.

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Textures are separated into foliated and non-foliated categories. Foliated rock is a product of differential stress

that deforms the rock in one plane, sometimes creating a plane of cleavage. For example, slate is a foliated

metamorphic rock, originating from shale. Non-foliated rock does not have planar patterns of strain.

Rocks that were subjected to uniform pressure from all sides, or those that lack minerals with distinctive growth

habits, will not be foliated. Slate is an example of a very fine-grained, foliated metamorphic rock, while phyllite

is medium, schist coarse, and gneiss very coarse-grained. Marble is generally not foliated, which allows its use

as a material for sculpture and architecture.

13.3.2. Chemical reactions

Another important mechanism of metamorphism is that of chemical reactions that occur between minerals

without them melting. In the process atoms are exchanged between the minerals, and thus new minerals are

formed. Many complex high-temperature reactions may take place, and each mineral assemblage produced

provides us with a clue as to the temperatures and pressures at the time of metamorphism.

Metasomatism is the drastic change in the bulk chemical composition of a rock that often occurs during the

processes of metamorphism. It is due to the introduction of chemicals from other surrounding rocks. Water may

transport these chemicals rapidly over great distances. Because of the role played by water, metamorphic rocks

generally contain many elements absent from the original rock, and lack some that originally were present. Still,

the introduction of new chemicals is not necessary for recrystallization to occur.

13.4. Some types of metamorphism

Metamorphic rocks can be grouping into two groups on the base of areal expanding of the metamorphism (Fig.

2.10.).

Fig. 2.10. Genetic environments of metamorphic rocks

Regional metamorphism: It expands on big area.

Burial metamorphism (Plit, T):

When sedimentary rocks are buried to depths of several hundred meters, temperatures greater than 300oC may

develop in the absence of differential stress. New minerals grow, but the rock does not appear to be

metamorphosed. The main minerals produced are often the Zeolites. Burial metamorphism overlaps, to some

extent, with diagenesis, and grades into regional metamorphism as temperature and pressure increase.

Hydrothermal metamorphism at subduction zone: Mechanism of the metamorphism is very similar to the ocean-

floor metamorphism. But its reason is the orogenic magmatism.

Hydrothermal metamorphism at geothermal region: Metamorfism gears to the volcanic, post-volcanic processes.

But these are local events usually.

14. Local metamorphism:

It expands on small area.

Contact metamorphism: It is the name given to the changes that take place when magma is injected into the

surrounding solid rock (country rock). The changes that occur are greatest wherever the magma comes into

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contact with the rock because the temperatures are highest at this boundary and decrease with distance from it.

Around the igneous rock that forms from the cooling magma is a metamorphosed zone called a contact

metamorphism aureole. Aureoles may show all degrees of metamorphism from the contact area to

unmetamorphosed (unchanged) country rock some distance away. The formation of important ore minerals may

occur by the process of metasomatism at or near the contact zone. When a rock is contact altered by an igneous

intrusion it very frequently becomes more indurated, and more coarsely crystalline. Many altered rocks of this

type were formerly called hornstones, and the term hornfels is often used by geologists to signify those fine

grained, compact, non-foliated products of contact metamorphism. A shale may become a dark argillaceous

hornfels, full of tiny plates of brownish biotite; a marl or impure limestone may change to a grey, yellow or

greenish lime-silicate-hornfels or siliceous marble, tough and splintery, with abundant augite, garnet,

wollastonite and other minerals in which calcite is an important component. A diabase or andesite may become

a diabase hornfels or andesite hornfels with development of new hornblende and biotite and a partial

recrystallization of the original feldspar. Chert or flint may become a finely crystalline quartz rock; sandstones

lose their clastic structure and are converted into a mosaic of small close-fitting grains of quartz in a

metamorphic rock called quartzite.

14.1. Texture of metamorphic rocks

In metamorphic rocks individual minerals may or may not be bounded by crystal faces. Those that are bounded

by their own crystal faces are termed idioblastic. Those that show none of their own crystal faces are termed

xenoblastic. From examination of metamorphic rocks, it has been found that metamorphic minerals can be listed

in a generalized sequence, known as the crystalloblastic series, listing minerals in order of their tendency to be

idioblastic. In the series, each mineral tends to develop idioblastic surfaces against any mineral that occurs lower

in the series. This series can, in a rather general way, enable us to determine the origin of a given rock. For

example a rock that shows euhedral plagioclase crystals in contact with anhedral amphibole, likely had an

igneous protolith, since a metamorphic rock with the same minerals would be expected to show euhedral

amphibole in contact with anhedral plagioclase.

Another aspect of the crystalloblastic series is that minerals high on the list tend to form porphyroblasts (the

metamorphic equivalent of phenocrysts), although K-feldspar (a mineral that occurs lower in the list) may also

form porphyroblasts. Porphyroblasts are often riddled with inclusions of other minerals that were enveloped

during growth of the porphyroblast. These are said to have a poikioblastic texture.

Most metamorphic textures involve foliation. Foliation is generally caused by a preferred orientation of sheet

silicates. If a rock has a slatey cleavage as its foliation, it is termed a slate, if it has a phyllitic foliation, it is

termed a phyllite, if it has a shistose foliation, it is termed a schist. A rock that shows a banded texture without a

distinct foliation is termed a gneiss. All of these could be porphyroblastic (i.e. could contain porhyroblasts).

A rock that shows no foliation is called a hornfels if the grain size is small, and a granulite, if the grain size is

large and individual minerals can be easily distinguished with a hand lens.

14.2. Classification of metamorphic rocks

Relative terms such as high-temperature or low-pressure are often used to refer to the physical conditions of

metamorphism but without precise designation of the temperatures and pressures involved. In order to maintain

similarity of meaning it is proposed that the whole spectrum of temperature conditions encountered in

metamorphism be divided into five parts, and the corresponding metamorphism may be designated as: very low-

, low-, medium-, high-, very high-temperature metamorphism. Likewise the broad range of pressure conditions

may be divided into five to give: very low-, low-, medium-, high-, very high-pressure metamorphism. In the

highest part of the very high pressure ultra-high-pressure metamorphism may be distinguished. The whole range

of P/T ratios encountered may be divided into three fields (radial sectors in a PT diagram) to give: low, medium,

high, P/T metamorphism.

The term metamorphic grade is widely used to indicate relative conditions of metamorphism, but it is used

variably. Within a given metamorphic area, the terms lower and higher grade have been used to indicate the

relative intensity of metamorphism, as related to either increasing temperature or increasing pressure conditions

of metamorphism or often both. To avoid this it is recommended that metamorphic grade should refer only to

temperature of metamorphism, following Winkler (1974, 1976). If the whole range of temperature conditions is

again divided into four, then we may refer to very low, low, medium, high, grade of metamorphism (Fig. 2.11.).

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Fig. 2.11. Winkler’s metamorphic system

14.3. Metamorphic Facies

The concept of metamorphic facies was first proposed by Eskola (1915) who gave the following definition: A

metamorphic facies is "a group of rocks characterised by a definite set of minerals which, under the conditions

obtaining during their formation, were at perfect equilibrium with each other. The quantitative and qualitative

mineral composition in the rocks of a given facies varies gradually in correspondence with variation in the

chemical bulk composition of the rocks".

It is one of the strengths of the metamorphic facies classification that it identifies the regularities and

consistencies in mineral assemblage development, which may be related to P-T conditions, but does not attempt

to define actual pressures and temperatures. Eskola (1920, 1939) distinguished eight facies, namely: greenschist,

epidote-amphibolite, amphibolite, pyroxene-hornfels, sanidinite, granulite, glaucophane-schist and eclogite

facies. Todays people use more metamorphic facies than Eskola, but his system usefull in the modern petrology

also (Fig. 2.12.).

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Fig. 2.12. Position of metamorphic facies in the P-T diagram

14.4. Protolith

Protolith refers to the original rock, prior to metamorphism. In low grade metamorphic rocks, original textures

are often preserved allowing one to determine the likely protolith. As the grade of metamorphism increases,

original textures are replaced with metamorphic textures and other clues, such as bulk chemical composition of

the rock, are used to determine the protolith.

If a rock has undergone only slight metamorphism such that its original texture can still be observed then the

rock is given a name based on its original name, with the prefix meta- applied. For example: metabasalt,

metagraywacke, meta-andesite, metagranite.

14.5. Metamorphic rocks with characteristic texture

These are the most common methamorphic rocks with characteristic texture. These texture is determined by the

metamorphic environment (pressure and temperature) and the protolith.

Slate: Slates form at low metamorphic grade by the growth of fine grained chlorite and clay minerals. The

preferred orientation of these sheet silicates causes the rock to easily break along the planes parallel to the sheet

silicates, causing a slatey cleavage. Note that in the case shown here, the maximum stress is applied at an angle

to the original bedding planes, so that the slatey cleavage has developed at an angle to the original bedding.

Phyllite: Phyllite composes quartz, sericite mica, and chlorite; the rock represents a gradation in the degree of

metamorphism between slate and mica schist. Phyllite is formed from the continued metamorphism of slate. The

protolith (or parent rock) for a phyllite is a shale or pelite.

Schist: The size of the mineral grains tends to enlarge with increasing grade of metamorphism. Eventually the

rock develops a near planar foliation caused by the preferred orientation of sheet silicates (mainly biotite and

muscovite). Quartz and Feldspar grains, however show no preferred orientation. The irregular planar foliation at

this stage is called schistosity.

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Mica-schist: It’s a special type of schists. Mica content is more than 50% and it has a high quartz content.

Gneiss: As metamorphic grade increases, the sheet silicates become unstable and dark colored minerals like

hornblende and pyroxene start to grow. These dark colored inerals tend to become segregated in distinct bands

through the rock, giving the rock a gneissic banding. Because the dark colored minerals tend to form elongated

crystals, rather than sheet- like crystals, they still have a preferred orientation with their long directions

perpendicular to the maximum differential stress.

14.6. Rocks of contact metamorphism

Contact metamorphism occurs adjacent to igneous intrusions and results from high temperatures associated with

the igneous intrusion. Since only a small area surrounding the intrusion is heated by the magma, metamorphism

is restricted to a zone surrounding the intrusion, called a metamorphic aureole. Outside of the contact aureole,

the rocks are unmetamorphosed. The grade of metamorphism increases in all directions toward the intrusion.

Mud protoliths: Many altered rocks of this type were formerly called hornstones, and the term hornfels is often

used by geologists to signify those fine grained, compact, non-foliated products of contact metamorphism. Shale

may become a dark argillaceous hornfels, full of tiny plates of brownish biotite

Carbonate protoliths: If the intruded rock is rich in carbonate the result is a skarn. Skarns and tactites are most

often formed at the contact zone between intrusions of granitic magma bodies into contact with carbonate

sedimentary rocks such as limestone and dolostone. Hot waters derived from the granitic magma are rich in

silica, iron, aluminium, and magnesium. These fluids mix in the contact zone, dissolve calcium-rich carbonate

rocks, and convert the host carbonate rock to skarn deposits in a metamorphic process known as

"metasomatism".

Sand protoliths: sandstones lose their clastic structure and are converted into a mosaic of small close-fitting

grains of quartz in a metamorphic rock called quartzite.

14.7. Retrograde metamorphism

If retrograde metamorphism were a common process then upon uplift and unroofing metamorphic rocks would

progressively return to mineral assemblages stable at lower pressures and temperatures. Yet, high grade

metamorphic rocks are common at the surface of the Earth and usually show only minor retrograde minerals.

Three factors inhibit retrograde metamorphism, two of which involve the fluid phase.

Selected literatures

Báldi T. 1991: Elemző (általános) földtan. – Nemzeti Tankönyvkiadó, Budapest, p. 797.

Balogh K. 1991: Szedimentológia I-II-III – Akadémiai Kiadó Budapest

Hartai É. 2003: A változó Föld. Egyetemi tankönyv. Miskolci Egyetemi Kiadó, p. 192.

Kubovics I. 1990: Kőzetmikroszkópia I-II. – Nemzeti Tankönyvkiadó, Budapest

Kubovics I. 2008: Általános kőzettan. A földövek kőzettana. – Mundus Magyar Egyetemi Kiadó, Budapest, p.

652.

Szakmány Gy. - Józsa S. 2008: Segédanyag BSc szakosok geológus szakirány magmás kőzettan gyakorlat

anyagához. – Kézirat, p. 28.

Szakmány Gy. 2008: Segédanyag BSc szakosok geológus szakirány üledékes kőzettan gyakorlat anyagához. –

Kézirat, p. 22.

Szakmány Gy. 2008: Segédanyag BSc szakosok geológus szakirány metamorf kőzettan gyakorlat anyagához. –

Kézirat, p. 30.

Wallacher L. 1992: Üledékes kőzetek és kőzetalkotó ásványaik I.-II. – Tankönyvkiadó, Budapest

Wallacher L. 1993: Magmás és metamorf kőztetek. - Nemzeti Tankönyvkiadó, Budapest

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http://geology.com

http://www.tulane.edu/EENS

Mineralogical exhibition of Mátra Museum

The mineralogical exhibition of Mátra Museum represents the minerals which are origined from magmatic

processes.

The intermediate basement of the Mátra Mountains is made up of the Dinarian-related Bükk Structural Unit.

This was subsided into a depth of 1500-3000 m however to the south of the village of Sirok, Jurassic formations

of the Western Bükk Mountains crop out. On the Darnó Hill and on the southern side of the Tarna Valley,

pillow lava structured Mesozoic basalt, siltstone and radiolarite are found in which various aged limestone

blocks are present. Because of metamorphic processes arose epidote, prehnite, albite, chalcite and dolomite on

the wall of the cracks. Minerals of sulphure can be found in several localities of metabasites.

Following a long phase of lifting and denudation, a new sediment cycle began at the end of the Eocene. Into this

gradually subsiding marine environment deposited the Eocene volcanic complex of Recsk. In the NE part of the

Mátra Mountains, NW to the Darnó Line, on the surface or near surface, (Upper Eocene to Middle Oligocene)

igneous-volcanic formations can be found. Their rocks are subduction volcanic island arc type products lime

alkaline igneous-volcanic andesite-dacitic in composition intruding in 4 or 5 cycles comprising subvolcanic-

intrusive bodies and strato-volcanic sheets. Sub-volcanic andesite diorite-porphyritic intrusions are the sources

of the so-called porpyritic copper ore formation and copper-polymetallic skarnic ores formed at the contact of

old carbonate rocks, as well as hydrothermal pyrite-precious metal ore deposits present in strato-volcanic

andesite. The paleogene sedimentary stage closed during the Eggenburgian stage in the Miocene with a

complete accretion of the sea basin and the emergence of a continental environment.

Sediments of the Neogene sea transgression in the second half of the Ottnangian were deposited only in the area

of the mountains and at the northern foregrounds. At the end of the Carpathian stage, the sea started to shallow.

The Mátra Mountains built up during the Badenian stage materials of several eruption centres elevated from the

shallow sea forming a peninsula adherent to the land of the southern foreground. This volcanism formed in a

quasi E-W-trending, gradually subsiding volcano-tectonic trench, is characterised by rhyolitic-dacitic, later

andesite lime alkaline volcanism repeated at several cycles during 7 million years between the Ottnangian and

Sarmatian stages. Resulting from the southern tilt of the Mátra in the Late Miocene, the mountains indicate, at

present, an apperenty asymmetryc structure defined by Lower Badenian (15-16 million years ago) multiply

alternating stratovolcanic products of great masses of lava and fine-coarse-grained volcanoclastite and

hialoclastite originating mainly from submerged eruptions. The present main ridge of the Western Mátra can be

considered as an eroded rim of a former large andesite volcano with a base diameter of ca. 13 km jointed by

parasite craters. The total thickness of the series containing the repeated alternations of volcanic lava and

volcanoclastite, according to data from deep drillings, can even be 1500-2000 m. In the Carpathian-Badenian

lime alkaline andesite, into the centre of the former volcanic structure collapsed in several ringshaped blocks

and pieces were intruded, above them hydrothermal-epithermal vein precious ore containing polymetallic ore

deposits (Gyöngyösoroszi, Parádsasvár) are present. In the final stage of volcanism, during the Sarmatian stage,

basaltic andesites fissure volcanic in origin were formed covering the ridge of the Mátra Mountains. Inside the

former craters, freshwater lakes were formed (e.g. the diatomite quarry of Szurdokpüspöki). From the siliceous

springs arisen during the post-volcanic activity and in smaller or larger lakes formed around them, geyserite and

limnoquartzite were separated out. These springs could be related to the formation of quartz and calcite veins

containing coloured ores.

Selected literatures

Gasztonyi É. 2010: A Mátra hegység ércesedése. – In: Baráz Cs. (szerk.) 2010. A Mátrai Tájvédelmi Körzet.

Heves és Nógrád határán. – Eger, 53-63.

Hartai É. 2003: A változó Föld. – Egyetemi tankönyv. Miskolci Egyetemi Kiadó, p. 192.

Juhász Á. 1987: Évmilliók emlékei. – Gondolat Kiadó, Budapest, 438-445.

Kiss J. 1982: Ércteleptan I. – II. – Tankönyvkiadó, Budapest, p. 731.

Szakáll S. 2010: A Mátra ásványtani jellemzése. – In: Baráz Cs. (szerk.) 2010: A Mátrai Tájvédelmi Körzet.

Heves és Nógrád határán. – Eger, 65-77.

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Szakáll S. - Jánosi M. 1995: Magyarország ásványai. - A Herman Ottó Múzeum állandó ásványtani kiállításának

vezetője. Miskolc, Herman Ottó Múzeum, p. 117.

Zelenka T. 2010: A Mátra hegység paleogén és neogén vulkanizmusa. – In: Baráz Cs. (szerk.) 2010: A Mátrai

Tájvédelmi Körzet. Heves és Nógrád határán. – Eger, 27-38.

MINERALOGICAL AND PETROLOGICAL FIELD TRIP TO THE SOUTHERN PART OF THE MÁTRA

MOUNTAINS

Route: Eger – Verpelét – Domoszló – Abasár – Gyöngyös – Gyöngyössolymos – Gyöngyöstarján –

Szurdokpüspöki – Gyöngyös – Kápolna – Kerecsend – Eger (140 km) (Fig. 4.1.)

Fig. 4.1. Topographical map of the one-day field trip at Mátra Mountains

Aims: To observe and to collect felsic and intermedier vulcanits, and vulcanosediment rocks, of the South-Mátra

region. To study the mineral associations, which are connected to the volcanits. To collect quartz varieties and

sedimentary silicate rocks, which are significant to that area and to take geomorphological observations.

It is important to take care of your and of the others’ physical soundness during the field trip!

15. Geology of the Mátra Mountains

The intermediate basement of the Mátra Mountains is made up of the Dinarian-related Bükk Structural Unit.

This was subsided into a depth of 1500-3000 m however to the south of the village of Sirok, Jurassic formations

of the Western Bükk Mountains crop out. On the Darnó Hill and on the southern side of the Tarna Valley,

pillow lava structured Mesozoic basalt, siltstone and radiolarite are found in which various aged limestone

blocks are present.

Following a long phase of lifting and denudation, a new sediment cycle began at the end of the Eocene. Into this

gradually subsiding marine environment deposited the Eocene volcanic complex of Recsk. In the NE part of the

Mátra Mountains, NW to the Darnó Line, on the surface or near surface, (Upper Eocene to Middle Oligocene)

igneous-volcanic formations can be found. Their rocks are subduction volcanic island arc type products lime

alkaline igneous-volcanic andesite-dacitic in composition intruding in 4 or 5 cycles comprising subvolcanic-

intrusive bodies and strato-volcanic sheets. Sub-volcanic andesite diorite-porphyritic intrusions are the sources

of the so-called porpyritic copper ore formation and copper-polymetallic skarnic ores formed at the contact of

old carbonate rocks, as well as hydrothermal pyrite-precious metal ore deposits present in strato-volcanic

andesite. The paleogene sedimentary stage closed during the Eggenburgian stage in the Miocene with a

complete accretion of the sea basin and the emergence of a continental environment.

Sediments of the Neogene sea transgression in the second half of the Ottnangian were deposited only in the area

of the mountains and at the northern foregrounds. At the end of the Carpathian stage, the sea started to shallow.

The Mátra Mountains built up during the Badenian stage materials of several eruption centres elevated from the

shallow sea forming a peninsula adherent to the land of the southern foreground. This volcanism formed in a

quasi E-W-trending, gradually subsiding volcano-tectonic trench, is characterised by rhyolitic-dacitic, later

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andesite lime alkaline volcanism repeated at several cycles during 7 million years between the Ottnangian and

Sarmatian stages. Resulting from the southern tilt of the Mátra in the Late Miocene, the mountains indicate, at

present, an apperenty asymmetryc structure defined by Lower Badenian (15-16 million years ago) multiply

alternating stratovolcanic products of great masses of lava and fine-coarse-grained volcanoclastite and

hialoclastite originating mainly from submerged eruptions. The present main ridge of the Western Mátra can be

considered as an eroded rim of a former large andesite volcano with a base diameter of ca. 13 km jointed by

parasite craters. The total thickness of the series containing the repeated alternations of volcanic lava and

volcanoclastite, according to data from deep drillings, can even be 1500-2000 m. In the Carpathian-Badenian

lime alkaline andesite, into the centre of the former volcanic structure collapsed in several ringshaped blocks

and pieces were intruded, above them hydrothermal-epithermal vein precious ore containing polymetallic ore

deposits (Gyöngyösoroszi, Parádsasvár) are present. In the final stage of volcanism, during the Sarmatian stage,

basaltic andesites fissure volcanic in origin were formed covering the ridge of the Mátra Mountains. Inside the

former craters, freshwater lakes were formed (e.g. the diatomite quarry of Szurdokpüspöki). From the siliceous

springs arisen during the post-volcanic activity and in smaller or larger lakes formed around them, geyserite and

limnoquartzite were separated out. These springs could be related to the formation of quartz and calcite veins

containing coloured ores.

As a consequence of the region’s overall southern tilt, Sarmatian-Pannonian formation can only be found at the

southern foot of the mountains. This movement continued during the Pannonian stage with the freshwater lake

replacing the Sarmatian sea covering an increasing area of the southern foothill. From the remnants of plants

accumulated in the resultant extensive marshlands, at some locations, thick lignite deposits formed.

The internal area of the mountains is covered mainly by Quaternary regolith, clay and red clay whereas valley

floors are filled by alluvial detritus. The burden of streams flowing from the mountains was deposited in the

foregrounds often in debris cones and alluvial cones.

16. 1st stop: Verpelét, Vár Hill, volcanic cone

One kilometer away from the settlement to the NW we can find the Vár Hill of Verpelét (Fig. 4.2.1.). It

heightens on the developed road which leads to Tarnaszentmária. The locality is situated between Verpelét and

Tarnaszentmária villages. The small volcanic cone can be seen from a great distance, can be easily approached

from the road. This is a protected area. Geographical coordinates of the hill are: 47°51’56.57”N, 20°12’46.39”E

(Fig. 4.2.2.).

Geographical position of

Verpelét, Vár Hill

Topographical map of

Verpelét and its environs

Geological formations of

Verpelét and its environs

The hill’s relative height is 58 m above the plain of the Tarna river valley.

It formed at the end of the Miocene age, during the final phase of the volcanism of the Matra. It was a central

type explosive volcano. Some reconstruction models show that the tiny volcano cone could be one of the

parasitic craters of the Matra. Their formations belong to the Nagyharsány Andesite Formation (Fig. 4.2.3.).

Rocks of these formation – pyroxene andesite and pyroxene andesite tuff – build up the central part of the Mátra

Mountains. These rocks are Badenian in age.. At the entry of the strip pit of the hill can be observed a complete

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stratovolcanic system. The volcanic activity, was characterized by mixed, effusive and explosive processes. The

lava plug, which filled the crater, had been spirited away by the mining. The hill’s most beautiful volcanic

layers’ formation can be observed as crossing through the entrance of the lower mine yard. The grain size of the

clasts decreases from the centre to the outer part of the volcano. . It can be well observed on the two sides of the

road which leads to the former mine yard. Its lava rock’s substance froms a transition between the dacite and the

andesite. The literature says that really nice, special designed opal could be find in the cracks of the crater’s

substance. Unfortunately these special opals had annihilated to nowadays by the collectors.

View of Verpelét,

Vár Hill from south

View of Verpelét,

Vár Hill from west

Road cut to the

former strip pit

North wall of the

quarry at Vár Hill

Western wall of the

quarry at Vár Hill

Strongly fragmented

andesite lava

Spheroidal jointed,

fragmented andesite

Spheroidal jointed,

fragmented andesite

(closer view)

Andesite blocks

cemented with

volcanic ash

View of Mátra

Mountains from the

Verpelét Vár Hill

17. 2nd stop: Domoszló, Tarjánka Gorge

The Tarjánka gorge is situated three kilometres to W-NW from Domoszló village. An access road opens from

the developed road. The Matra’s most spectacular gorge, the valley of the Tarjánka creek can be reached

through this acces road (Fig. 4.3.1.). The valley’s entrance is situated 800 m to the North from the developed

road. Geographical coordinates of the entry of the valley are: 47°50'27.97"N, 20°7'50.06"E (Fig. 4.3.2.).

Geographical position of

the Tarjánka gorge

Topographical map of

Domoszló and its environs

Geological map of

Domoszló and its environs

Tarjánka canyon exposes andesite lava flows and andesite pyroclastics, which belong to the Nagyharsány

Andesite Formation. The age of this formation is Middle Miocene, Badenian (Fig. 4.3.3.). Significant proportion

of the gorge’s rocks are pyroclasts, pyroxene andesite tuffs, lapilli stones, which continuity is interrupted by the

pyroxene andesite lava beds. The variable particle sized pyroclasts contain volcanic bombs and volcanic blocks

in big quantity. Their size is variable. The quarter cubic metered pieces are frequent too. These big sized blocks

clearly sign the proximity of the crater of a volcano. The bombs and the blocks represent different kinds of rock

types. The pyroclasts’ colour - depending on the alteration which took place during the post volcanic activity –

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can be light grey, yellowish grey, or cherry red. Good quality andesite had been mined in that nowdays

abandoned quarry, which lies at the south end of the valley. The interesting, rare mineral of the locality is the

hyalite which belongs into the group of quartz varieties.

According to the newest volcano morphological reconstructions, the Tarjánka gorge lies at the boundary of two

former volcanic cones, namely the Kékes-volcano and the Nagy-Szár-Hill one.

Abandoned andesite

quarry at the entrance

of Tarjánka gorge

Andesite blocks in the

wall of strip pit at the

abandoned andesite

quarry

Andesite volcanic

bomb with concentric

internal structure at the

northern part of the

strip pit

Graded

stratified surge

suites at the

western wall of

Tarjánka gorge

Unstratified lahar

sediment at the

western wall of

Tarjánka gorge

Narrow section of the

Tarjánka gorge

Volcanic bomb

embedded into

andesite lapillite

Lahar sediment without

internal structure

(macroscopic view)

Stricture at the

middle part of

Tarjánka gorge

Natural pool

deepened by

Tarjánka brook

18. 3rd stop: Gyöngyös, Farkasmály quarry

The two-storey quarry of Farkasmály is situated two kilometers away from the city of Gyöngyös to the North,

and 150 m away to the West from the road which connects Gyöngyös with Mátrafüred (Fig. 4.4.1.). Andesite

was mined here in the 20th century. Geographical coordinates of the quarry are: 47°47'40.87"N, 19°57'37.48"E

(Fig. 4.4.2.).

Geographical position of

the Farkasmály quarry

Topographical map of

Gyöngyös and its environs

Geological map of

Gyöngyös and its environs

Andesite pyroclastics are the most common rocks in the quarry. It’s a scorious andesite tuff with high lapilli

content. Scorious structure of lapilli shows the high volatile quantity of the lava. Pyroclastics refer to heavy

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explosive eruptions. The formations represent the clastic part of the Nagyharsányi Andezit Formation. The age

of these is Middle Miocene, Badenian (Fig. 4.4.3.). These pyroclastics could be the external mantle of Sárhegy

volcano.

The sequence has suffered strong oxidation dute to the high level of post volcanic activity, that’s why its colour

changed into brick red.

The rock had been used for building stone.

View of the Farkasmály

quarry

Andesite lapillite blocks

at the Farkasmály quarry

Eastern wall of

Farkasmály quarry

Andesite

blocks at the

eastern part of

the quarry

Fresh

discontinuity on

andesite lapillite

Andesite lapillite at the

Farkasmály quarry

Andesite lapilli and scorious andesite lapilli in

andesite lapillite at the northern part of the

Farkasmály quarry

19. 4th stop: Gyöngyössolymos, Bábakő

The locality can be found one km to the east from Gyöngyössolymos, and 100 m to the west from the developed

road, which connects Gyöngyös with Mátrafüred (Fig. 4.5.1.). Giant silicified cliffs build up this formation. This

type of rocks is very rare in Hungary and even in the Carpathian Basin. This is the reason because That’s why

the Bába-kő of Gyöngyössolymos is a strictly protected area. Geographical coordinates of Bábakő are:

47°48'54.88"N, 19°57'23.39"E (Fig. 4.5.2.).

Geographical position of

the Bába-kő at

Gyöngyössolymos

Topographical map of

Gyöngyössolymos and its

environs

Geological map of

Gyöngyössolymos and its

environs

The Bábakő, is consists of hydro-thermally silicified rhyolite cliffs (Fig. 4.5.3.). Their material dominantly

consists of quartzite. Quartz and chalcedony can occur in the rock which is soaked with silica. Such formations

form in the course of metasomatism during postvolcanic activity.

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Its most frequent type is the silicification when the rock’s material is almost compltely changed to SiO2. The

silicate rocks’ material, which formed in this way, is most frequently opal and chalcedony. It often occurs that

more mm, sometimes even 1-2 cm sized quartz-, amethyst- or even citrine crystals form in the rocks’ cavities.

This kind of process could happen mostly in the vicinity of active geysers. Accordingly we call these kind of

rocks: geyserites.

Trail to the Bába-kő

at Gyöngyössolymos

View of the Bába-kő

at Gyöngyössolymos

The biggest geyserite

cliff at the Bába-kő

The Bába-kő is built

up from silicified

rhyolite (geyserite)

Geyserite cliffs at

the Bába-kő

Geyserite, which

builds up the Bába-

kő

Weathered surface of

a geyserite cliff at the

Bába-kő

The geyserite is a

structureless rock,

built up from 7

hardness minerals

Weathering of the

geyserite is slow

because of its

hardness

Botryoidal

chalcedony in the

cavity of a geyserite

cliff at the Bába-kő

20. 5th stop: Gyöngyössolymos, Kis Hill

The hill-side, which lies 400 m away from the settlement to the northwest, is covered with a young forest (Fig.

4.6.1.). On its southwest side we can find the so called Lila-mine where hill building rhyolite is mined for

building and for coating. The Kis-hegy’s geographical coordinates: 47°49'34.20"É, 19°55'53.27"K (Fig. 4.6.2.).

Geographical position of

the Kis Hill at

Gyöngyössolymos

Topographical map of

Gyöngyössolymos and its

environs

Geological map of

Gyöngyössolymos and its

environs

The Kis Hill itself is built up from rhyolite. Its lava dome has been formed during the Late Miocene. This is a

light coloured rock with fluidal texture. During the end of the Badenian rhyolitic volcanism took place at several

parts of the Mátra Mountains. A part of the fluidal, litofisy, spheroidal rhyolite lava of the Kis-hegy of

Gyöngyössolymos flow into water. It is proved by the presence of the perlite which occured at the end of the

lava flow. The K/Ar age of the rhyolite is 15 million years. The formations belong to Gyöngyössolymos

Rhyolite Formation (Fig. 4.6.3.).

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Phreatomagmatic, vitreous lava, can be found near the top region of the hill. Whereas on the Southwest slope of

the hill lava flow residues can be observed. Strange shaped hooked structures can be found on the upper levels

of the lava stream. On the one hand its reason is that the viscous lava streamed into water. On the other hand

these particular curves could form due to the local lava stream’s congestion.

View of the Kis Hill at Gyöngyössolymos from

west

View of the Kis

Hill at

Gyöngyössolymos

from east

Lower part of

the southern

slopes of the

Kis Hill

Rhyolite lava

flows cover

large areas at

the southern

slope of the

Kis Hill

Deatail of a rhyolite lava flow at the

southern slope of the Kis Hill

Weathered surface

of a rhyolite lava

flow at the southern

slope of the Kis Hill

The surface of a

lava flow showing

fluidal texture

which characteristic

to the rhyolite at the

southern slope of

the Kis Hill.

Strongly

weathered

rhyolite

surface at the

southern slope

of the Kis Hill

Trail to the

rhyolite debris

at the

southeast slope

of the Kis Hill

Rhyolite debris at the southeast

slope of the Kis Hill

Rhyolite debris at

the southeast slope

of the Kis Hill;

closer view

Rhyolite blocks

with freshly broken

surface showing the

light colour and

fluidal texture of the

rock

Biotite crystals

on the surface

of a rhyolite

block

Rhyolite with

fluidal texture;

closer view

Fragments of a rhyolite lava flow at

the southwest slope of the Kis Hill

Lava flow with

fluidal internal

structure at the

southwest slope of

the Kis Hill

21. 6th stop: Gyöngyöstarján, Köves Hill

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There are several exposures in the vicinity of Gyöngyöstarján where the remains of the postvolcanic

hydrothermal processes of the Badenian volcanism can be studied (Fig. 4.7.1.). One of these localities is the

Köves-tető of Gyöngyöstarján. It can be found 1,5 km away from the village to the North, along the developed

road, which leads to the Oktatóház. Its geographical coordinates are : 47°49’52.06”N, 19°51’46.11”E (Fig.

4.7.2.).

Geographical position of

the Köves Hill at

Gyöngyöstarján

Topographical map of

Gyöngyöstarján and its

environs

Geological map of

Gyöngyöstarján and its

environs

There is a special sedimentary siliceous formation crops out to the surface here. It is the laminated geyserite.

This rock formed during the course of geysers activity. The varied compositioned silicate sheet give the

„stripped” arrangement of the rock. Mostly their material is chalcedony or opal, rarely agate. The small-statured,

clear quartz crystals are frequent in the cavities of the rock.

Another silicate rock, the hydro-quartzite, can be found directly next to the laminated geyserite. It hasn’t got

inner structure. Its material is SiO2. Rigid, shell-crushing rock. Supposingly it can be found directly near the

geyser, it condensed from small still water, (e.g.: ponds) due to chemical processes (Fig. 4.7.3.).

The Köves Hill lies

along the road

leading to the former

school house

Trail to the

abandoned quarry of

Köves Hill

View of the quarry at

Köves Hill

Hydroquartzite

exposure at the

southern part of the

Köves Hill quarry

Laminated geyserite

layers at the Köves

Hill quarry

Debris of laminated

geyserite and

hydroquartzite at the

Köves Hill quarry

Laminated geyserite

debris at the Köves

Hill quarry

New exposure of the

laminated geyserite

at the top of Köves

Hill

Laminated geyserite

at the Köves Hill

quarry; closer view

Jasper, chalcedony

and opal are the

building minerals of

the laminated

geyserite at the

Köves Hill quarry

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Jasper layer in the

laminated geyserite

at the Köves Hill

quarry

22. 7th stop: Gyöngyöstarján, Füledugó quarry

Füledugó quarry is situated at the northwest end of Gyöngyöstarján village (Fig. 4.8.1.). This is a big andesite

quarry which two levels consists of several strip pits in. Geographical coordinates of the locality are:

47°49'20.96"N, 19°51'32.69"E (Fig. 4.8.2.).

Geographical position of

the Füledugó quarry at

Gyöngyöstarján

Topographical map of

Gyöngyöstarján and its

environs

Geological map of

Gyöngyöstarján and its

environs

This quarry excavates broken and altered (argillizated, silicified) miocene andesite. These rocks belong to the

Nagyhársas Andesite Formation. The age of these successions is Badenian (Fig. 4.8.3.).

The original complexion and structure had been strongly changed by hydro thermal solutions, which percolate

on the rocks. The minerals are connected to thiner-thicker siliceoused veins in the andesite. Out of these, the

most famous are the chalcedony and the opal. The chalcedony fills in the cracks with 5.8 cm veins. Blue or gray,

often dropstone spheroidal or botryoidal in shape. Its pseudomrph after calcite, aragonite, or baryte often can be

found. The opal is an other dominant vein filling mineral, it appears in red, brown, yellowish, stout masses.

Rarely we can find aragonite, baryte and hematite at this locality, too.

Junction to the

Füledugó quarry at

Gyöngyöstarján

Road to the Füledugó

quarry at

Gyöngyöstarján

View of the strip pit,

with andesite walls in

the back

Andesite blocks at

the Füledugó quarry

Small sized andesite

debris at the

Füledugó quarry

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Trail to the upper,

mineral-rich strip pit

Mineral-rich rocks

are at the upper strip

pit

Hydrothermal altered

andesite at the upper

strip pit

Jasper vein in the

northern wall of the

quarry

Vertical opal vein in

the wall of the upper

strip pit

Jasper debris at the

upper strip pit of

Füledugó quarry

Brown coloured

opals at the upper

strip pit of Füledugó

quarry

A cavity formed in a

jasper block filled

with botryoidal

chalcedony

Jasper, opal and

chalcedony in the

wall of the upper

strip pit

A cavity within a

huge andesite block

encrusted by light-

blue chalcedony

Cavity filled by

jasper and opal in

andesite at the upper

strip pit of Füledugó

quarry

23. 8th stop: Szurdokpüspöki, diatomite quarry

The locality lies at the border of Nógrád and Heves Counties, between Szurdokpüspöki and Gyöngyöspata

villages (Fig. 4.9.1.). There is a special white coloured rock, which has very low specific weight. This rock is

the laminated diatomite. Geographical coordinates of the abandoned quarry are: 47°50’34.38”N, 19°43’49.91”E

(Fig. 4.9.2.).

Geographical position of

the diatomite quarry at

Szurdokpüspöki

Topographical map of

Szurdokpüspöki and its

environs

Geological map of

Szurdokpüspöki and its

environs

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The diatomic mud have been deposited during the Sarmathian. The sedimentational environment was shallow

marine lagunal environment. Marine water has a special composition because of the hydrothermal processes at

the Mátra Mountains. which can be explained with the enforcement of the post volcanic vehemence source’s

impacts of the Matra Mountains. The sedimentary pool had been mewed from the opened sea, so the diatoms

started to bloom in the water which contained a big amount of dissolved silicia. Millions of microscopic shells

of Diatomaceae alga compose the diatomite. The maximal thickness of diatomite succession is 100 m in the

vicinity of Szurdokpüspöki and Gyöngyöspata. The lower 40 m thick unit has been deposited in freshwater,

while the upper unit settled among marine circumstances. The layers of the abandoned quarry at

Szurdokpüspöki expose the lower unit. Here laminated diatomite and lymno-opalite, bentonite and andesite tuff

interbeddings can be observed. The relatively big amount of Hydrobia shells and the frequency of fish, plant-

and insect remains are characteristict to the lower complex. It is covered by a rhyolite tuff layer, which belongs

into the Galgavölgy Rhyolite Tuff Formation. We can find the so-called marine diatomaceous earth complex

above it in about 60 m thickness (Fig. 4.9.3.).

The entrance of the

diatomite quarry at

Szurdokpüspöki

Road to the strip pit

of the diatomite

quarry at

Szurdokpüspöki

The main strip pit of

the diatomite quarry

at Szurdokpüspöki

Northeast part of the

quarry where the

diatomite layers are

exposed

Debris of diatomite

at the quarry wall

Limnic opalite stripe

between two

diatomite layers

White coloured

diatomite layers at

the northeast part of

the quarry

Dark grey coloured

limnic opalite; closer

view

Limnic opalite is

harder than the

diatomite

The western side of

the quarry

Dendritic

manganese-oxide on

marl from the

western part of the

quarry

Light coloured

chalcedony at the

upper strip pit

Chalcedony and

agate spots in

silicified rocks

Mineral and rock collecting field trips in Hungary

24. Dunabogdány, Csódi Hill

Dunabogdárny is a medium-sized village at the northernp art of Visegrád Mountains, along the right bank of the

Szentendre branch of the river Danube (Fig. 5.1.1.). The 279 m high Csódi Hill south of the village has been the

site of intensive quarrying for more than150 years. The stone has been mostly used for construction and road

Mineralogy Petrology

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paving; nowadays it is used as aggregate and for river bank protection. The hill is a classical mineralogical

locality in Hungary. The geographicall coordinets are: 47°46’37.73”N, 19°02’15.01”E (Fig. 5.1.2.).

Fig. 5.1.1. Geographical

position of the of Csódi

Hill, Dunabogdány

Fig. 5.1.2. Topographical

map of Dunabogdány and

its environs

Fig. 5.1.3. Geological map

of Dunabogdány and its

environs

Csódi Hill is a typical laccolith, formed 14.8 million years ago during the Middle Miocene, produced by early

volcanism of Börzsöny and Visegrád Mountains (Fig. 5.1.3.). The ascending magma was unable to traverse the

Oligocene sedimentary strata, but uplifted and burned them. The contact metamorphic shales had been exposed

along Cs6di Creek previously.

The laccolith is made of dacite (earlier considered as andesite). Fresh rock is bluish grey, while hydrothermal

alteration yielded yellowish brown colour. The fine-grained matrix embeds plagioclase feldspars, biotite, and

amphibole. Garnet (almandine) is also scattered in the matrix.

Xenoliths in dacite, characterised by a special mineral assemblage formed by the thermal effect of ascending

magma to the enclosed carbonate basement rock fragments and by later hydrothermal activity. The characteristic

components of the enclaves are brucite, serpentine minerals, hydrogrossulars, mectite, and calcite.

Cooling of the laccolith produced characteristic tangential joints and radial fissures.

The first precipitates on fissure walls ar members of a hypothermal paragenesis overgrown crystals of the rock

forming minerals. However, the mineralogical character of Csódi Hill is determined by the hydrothermal

minerals. They include zeolites of worldwide reputation (chabazite-Ca and its twin variety, "phacolite", stilbite-

Ca, and analcime). Various calcite generations accompany the fissure-filling zeolites. The last precipitates are

epigenetic (secondary) minerals, mostly Mn and Fe oxides (hydroxides) (goethite, hematite).

All these minerals were discovered by large-scale quarrying.

View of the Csódi

Hill at Dunabogdány,

from east

Detail of the quarry

at Csódi Hill

Csódi Hill is a dacite

laccolith

Fragmented dacite at

the lower quarry

Light coloured

dacite in the quarry

of Csódi Hill,

Dunabogdány

Bedded dacite at the

southern part of the

Bedded dacite at the

southern part of the

Banded structure in

dacite

Dacite has

porphyritic texture

Cavity encrusted by

limonite in dacite

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strip pit at

Dunabogdány strip pit (closer view)

Cavity encrusted by

limonite in dacite

(closer view)

Chabazite is a

common mineral in

the cavities of dacite

Spot-like mineral

aggregations in

dacite

Grown-up crystals of

plagioclase feldspar

on dacite

Grown-up crystals

of plagioclase

feldspar on dacite

(closer view)

Grow-up crystals on

dacite

Calcite crystals in the

cavity of dacite

Yellow coloured

calcite in dacite

Selected literatures

Bognár L. 1987: Ásványhatározó. – Gondolat Kiadó, Budapest, p. 478.

Juhász Á. 1987: Évmilliók emlékei. – Gondolat Kiadó, Budapest, 405-411.

Szakáll S. (szerk.) 1996: 100 magyarországi ásványlelőhely. – Minerofil Kiskönyvtár II., p. 139.

Szakáll S. 2008: Barangolás az ásványok világában. – Debrecen, p. 120.

Szakáll S. – Jánosi M. 1995: Magyarország ásványai. Kiállításvezető. – Miskolc, 68-75.

Vendl A. 1926: Jelentés Szentendre, Leányfalu, Dunabogdány és Pomáz környékéről. - A Magyar Kir. Földtani

Intézet évi jelentése 1924-ről, 31, 21-22.

25. Erdőbénye, Mulató Hill, andesite qarry

One of Hungary’s most famous mineral collecting site can be found at the Mulató-hill which rises near

Erdőbénye (Fig. 5.2.1.). To the abandoned quarry the easiest way is from Bodrogkeresztúr.It can be found

directly on the right side of the road turning off from the number 37 road toward Erdőbénye. The abandoned

quarry’s lower floor is filled up with water, forming a lake, but the upper floor can be easily studied. Its

geogrophical coordinates are: 48°15’26.95”N, 21°21’33.64”E (Fig. 5.2.2.).

Fig. 5.2.1. Geographical

position of the of

Erdőbénye, Mulató Hill

Fig. 5.2.2. Topographical

map of Erdőbénye and its

Fig. 5.2.3. Geological map

of Erdőbénye and its

environs

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environs

The Mulató-hill – Brown máj formed during the end of the Miocene age (Late Sarmatian). Later its material has

been prepared ou forming a laccolith. The magma pushed in to a slightly older rhyolite tuff and melted that

along the contact zone. Sarmatian plant casts can be found in the „burnt”shale of the sometimes occurring

clayey tufit. The laccolith’s rock material is pyroxene andesite. There are varied mineral associations occur in its

spheroidal cavities, which most frequent members are the quartz species and carbonates. Also, many accessory

minerals appear there, especially in the small cavities (Fig. 5.2.3.).

These are the most frequent minerals in the andesite cavities:

Cristobalite: milk-white, mm about octahedron-like crystals with tridimite.

Goethite: brown, earthy-aggregations, encrustments and pseudomorph after siderite.

Hornblende: black, mm columnar-acicular crystals, with tridimit.

Calcite: white, cm reaching romboeders and spheres.

Quartz: colourless, mm crystal encrustments

Opal: white, bluish white, green, glassy drop stone like or spherical aggregates.

Saponine („mauritzit”): black, matte surfaced crusts, mm tubular sets.

Siderite: brown, tan, cm more spherical, reniform and radial sets, encrustments, and a few mm romboeders.

Tridimite: white, yellowish, 1-3 mm tabular crystals, fan shaped crystal groups

Detail of the

abandoned quarry of

Mulató Hill,

Erdőbénye

Deep lake fills up the

former lower strip pit

Fragmented, bedded

pyroxene-andesite at

Mulató Hill

The Mulató Hill is

built up from bedded

pyroxene-andesite

A pyroxene-andesite

wall at the Mulató

Hill quarry

Vertical parting

pyroxene-andesite at

the Mulató Hill

quarry

Minerals often occur

in the debris of

pyroxene-andesite

Cavities filled with

minerals in

pyroxene-andesite

Giant cavity

encrusted by calcite

in pyroxene-andesite

Siderite is one of the

most common

mineral in the

cavities of

pyroxene-andesite

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1,5 cm diameter

spheroidal siderite in

the cavity of

pyroxene-andesite

Spheroidal siderite in

the cavity of

pyroxene-andesite

Spheroidal siderite

and calcite on the

wall of a cavity of

pyroxene-andesite

Cavity covered by

spheroidal siderite

and calcite

Spheroidal siderite

in the cavity of

pyroxene-andesite

Spheroidal siderite

crystals

Separated spheroidal

siderite in the cavity

of pyroxene-andesite

Spheroidal calcite

coloured by limonite

in pyroxene-andesite

Big spheroidal

calcite in the

pyroxene-andesite of

Mulató Hill

Spheroidal calcite in

the cavity of

pyroxene-andesite

Spheroidal calcite

crystals in the cavity

of pyroxene-andesite

Selected literatures

Bognár L. 1987: Ásványhatározó. – Gondolat Kiadó, Budapest, p. 478.

Juhász Á. 1987: Évmilliók emlékei. – Gondolat Kiadó, Budapest, 172-173., 463-470.

Szakáll S. (szerk.) 1996: 100 magyarországi ásványlelőhely. – Minerofil Kiskönyvtár II., p. 139.

Szakáll S. 2007: A Tokaji-hegység ásványtani jellemzése. – In: Baráz Cs. – Kiss G. (szerk.) 2007: A Zempléni

Tájvédelmi Körzet. Abaúj és Zemplén határán. – Eger, 45-54.

Szakáll S. 2008: Barangolás az ásványok világában. – Debrecen, p. 120.

Szakáll S. – Jánosi M. 1995: Magyarország ásványai. Kiállításvezető. – Miskolc, 26-35.

26. Felsőcsatár, greenschist quarry

The greenschist quarry of Felsőcsatár is a temporary active mine. It can be found directly along the street

between the village and the talk mine (Fig. 5.3.1.). The here exposed low grade metamorphic rocks, belong into

the Kőszeg–Rechnitz series The site’s geographical coordinates are: 47°12’28.01”N, 16°26’54.77”E (Fig.

5.3.2.).

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Fig. 5.3.1. Geographical

position of the greenschist

quarry at Felsőcsatár

Fig. 5.3.2. Topographical

map of Felsőcsatár and its

environs

Fig. 5.3.3. Geological map

of Felsőcsatár and its

environs

The Kőszeg Hills is the east part of the Kőszeg Rechnitz Mountains which reaches over Hungary. Accordingly,

it’s geology is just like the areas which are at the Austrian parts. The locality’s material formed during the

Mesozoic. Its metamorphic process took place in the Tertiary period. Its slate series is a relative of the high-

Tauern’s „pennine” shale series. The quarry of Felsőcsatár exposes this series’s greenschist formations which

are strongly slatied and fragmented. The greenschist was formed with the modification and metamorphoses of

volcanic rocks. With naked eye, minerals can be hardly seen, but using microscope, amphibole species,

actinolite, albite, chlorite scales and epidote can be observed in the rock. Rarely it contains ore minerals, firstly,

pyrite and iron sulphides. Veins in the greenschist’s separation planes often, filled up with white quartz and

albite. These minerals are connected to the above mentioned veins (Fig. 5.3.3.).

The most frequent minerals which can be collected in the greenschist quarry of Felsőcsatár:

Actinolite: dark green, cm columnar crystals, often aggregates in the vicinity of the veins

Albite: white, stout masses with quartz and 1-3 mm tabular crystals in the cavities

Goethite: tan patches, coatings.

Calcite: white, stout aggregates in the veins.

Chlorite: green, mm scales in the rock and at the edge of the veins

Quartz: firstly it appears stouty in the veins; they are only a few mm crystals in the cavities

Malachite: green, dust-like sandings.

Pyrite, calcopyrite: particles, sandings and 1-2 mm pyrite-hexaeders.

View of the

greenschist quarry at

Felsőcsatár

The strip pit of the

greenschist quarry at

Felsőcsatár

Steep wall of the

greenschist quarry at

Felsőcsatár

Detail of the northern

part of the quarry

Fragmented and

foliated greenschist

succession at the

northern part of the

quarry

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Greenschist is a well

crumbling

metamorphic rock

with foliated texture

Thick greenschist

succession at the

Felsőcsatár quarry

Foliated structure

greenschist block in

the quarry

Foliated greenschist

at the Felsőcsatár

quarry

Greenschist debris

at the strip pit

Pieces of greenschist

are prepared to be

polished

Greenschist is an

important local

building stone at

Felsőcsatár

Greenschist is often

used for coating the

footing of buildings

Selected literatures

Bognár L. 1987: Ásványhatározó. – Gondolat Kiadó, Budapest, p. 478.

Juhász Á. 1987: Évmilliók emlékei. – Gondolat Kiadó, Budapest, 306-310.

Szakáll S. (szerk.) 1996: 100 magyarországi ásványlelőhely. – Minerofil Kiskönyvtár II., p. 139.

Szakáll S. 2008: Barangolás az ásványok világában. – Debrecen, p. 120.

Szakáll S. – Jánosi M. 1995: Magyarország ásványai. Kiállításvezető. – Miskolc, 106-111.

Varrók K. 1955: Felsőcsatár környékének földtani felépítése, talkum- és vasérc-előfordulásai. - A Magyar

Állami Földtani Intézet évi jelentése 1953-ról, II., 479-489.

27. Kisnána, andesite quarry

The locality can be approached on the Eger, Verpelét, Kisnána, Domoszló, Gyöngyös route by bus (Fig. 5.4.1.).

The bus have to be left in the station before László Móré’s castle which is Kisnána’s notable historical

building.The road which leads to the quarry is directly in the opposite of the castle.The mine’s area can be found

1 km away from kisnána to the North, about 220 m height above sea level. The quarry’s southern part lies

directly to the Hátsó-Tarnóca-creek. Its North-South extension is 200 meters, and its East-West extension is:400

metres. The locality’ geographical coordinates are: 47°52’00.61”N, 20°09’13.89”E (Fig. 5.4.2.).

Fig. 5.4.1. Geographical

position of the Kisnána,

andesite quarry

Fig. 5.4.2. Topographical

map of Kisnána and its

Fig. 5.4.3. Geological map

of Kisnána and its

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environs environs

The quarry exposes Miocene, fine-grained, dark grey pyroxene-andesite. This rock formed during the main

volcanic activity of the region, some 15-16 million years before. In the black, fresh andesite, which can be found

at the lower part of the quarry, there are cm, furthermore dm measured bladder cavities occur. There are two

mineral formation processes took place in the pyroxene-andesite of Kisnána. An exhalitive mineral formation

and a hydrothermal one (Fig. 5.4.3.).

The most frequent minerals of the locality:

Aragonite: colourless, elongated columnar, acicular, crystal groups, respectively pink, soemtimes completely

filling up the cavities. Their length can reach 10 cm.

Barite: colourless, 1-3 mm tabs.

Biotite: 1-2 mm fulvous, black, hexagonal lamellar crystals.

Goethite: tan crusts, coatings, botryoidal, romboeders. It often appears as pseudomorph after siderite.

Hornblende: black, mm planked, acicular crystals.

Calcite: white, yellow or greenish romboeders, spherical aggregates and encrustments.

Clinoptilolite: colourless, mm tabular crystals. It often occures with saponine.

Quartz: colourless, 1-2 mm columnar crystals, respectively more cm stout inclusions.

Mn-oxides: purplish brown lamellar sets, respectively black spheres and encrustments.

Montmorillonite: white or slightly coloured, fat touching, predominantly very fine grains.

Opal: tan stout masses.

Saponine: light green, greyish, earthy nests, clay-like masses

Siderite: light brown, greyish brown, dark brown, sometimes vigorously colour playing surfaced romboeders,

spheres and encrustments.

Tridimite: yellowish, 1-2 mm tabular, fan-like or star shaped groups.

Detail of the andesite

quarry at Kisnána

The mineral-rich part

of the quarry at

Kisnána

Fragmented, bedded

andesite at the quarry

of Kisnána

Thin bedded, dark

coloured andesite at

the Kisnána quarry

Porphyritic textured,

dark coloured

andesite at Kisnána

Cavities in andesite

contain minerals in

great variety

Barite crystals in an

andesite cavity

Large quartz crystals

in an andesite cavity

Brown coloured opal

from Kisnána

Botryoidal

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chalcedony from

Kisnána

Small barite crystals

in the cavity of the

andesite

Vitreous aragonite

crystals in andesite

Fibrous aragonite in

andesite

Spheroidal calcite in

andesite

Siderite crystals in

the cavity of the

andesite

Spherosiderite in the

cavity of the andesite

Manganese-oxide

encrustation on the

surface calcite

crystals

Selected literatures

Bognár L. 1987: Ásványhatározó. – Gondolat Kiadó, Budapest, p. 478.

Gasztonyi É. 2010: A Mátra hegység ércesedése. – In: Baráz Cs. (szerk.) 2010: A mátrai Tájvédelmi Körzet.

Heves és Nógrád határán. – Eger, 53-63.

Kern Z. 2007: Nemesopál, opál, faopál: a kisnánai lelet. – A Földgömb: a Magyar Földrajzi Társaság folyóirata,

9(1). 12-13.

Szakáll S. (szerk.) 1996: 100 magyarországi ásványlelőhely. – Minerofil Kiskönyvtár II., p. 139.

Szakáll S. 2008: Barangolás az ásványok világában. – Debrecen, p. 120.

Szakáll S. 2010: A Mátra ásványtani jellemzése. – In: Baráz Cs. (szerk.) 2010: A mátrai Tájvédelmi Körzet.

Heves és Nógrád határán. – Eger, 65-77.

Szakáll S. – Jánosi M. 1995: Magyarország ásványai. Kiállításvezető. – Miskolc, 44-56.

28. Pálháza, perlite quarry

Hungary’s largest perlite quarry, can be found 2 km away from Pálháza to the Southwest, at the Gyöngykő-hill

(Fig. 5.5.1.). It is worth to search for this site because of the rock, the perlite what can be found there. It is easy

to approach it with car, since it is an active mine, but the entry is licensed. The site’s geographical coordinates

are: 48°27'29.37"N, 21°29'42.85"E (Fig. 5.5.2.).

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Fig. 5.5.1. Geographical

position of the Pálháza,

perlite quarry

Fig. 5.5.2. Topographical

map of Pálháza and its

environs

Fig. 5.5.3. Geological map

of Pálháza and its environs

This special rock formed during rhyolite volcanic activity (Fig. 5.5.3.). It solidifies as obsidian or perlite

depending on the vulcanic glass’s water content. On the other hand, the less water content obsidian can turn into

perlite with water absorption along its micro-crack netting. The perlite is a stone beaded, tiny spherical

structured glassy rhyolite type. These spheres inside are often obsidian, which is a witness that the perlite

formed from the obsidian during its hypothermia along the crack netting.

The perlite gives away its water content with swelling to a 10-12 times bigger shape, when it is ignited to 1000

°C This feature causes its economical significance. The perlit’s high porosity is primarily as a result of thermal

and acoustic insulation. Its high SiO2 content, results the resistance to chemicals and as filter material utilized.

At the rhyolite areas, between Telkibánya-Nagyhuta and Baskó-Tolcsva two dozen smaller-bigger perlite

occurrences are known. Here, the SiO2 content of the perlite changes between 68-74 percents.

The largest perlite

quarry of Hungary

can be found at

Pálháza

Perlite is mined in

staged system at the

quarry

Detail of the strip pit

of the perlite quarry

at Pálháza

Detail of perlite

quarry at Pálháza

This is an active

quarry, perlite is

mined recently

Vent-filling lava at

the perlite quarry

Prismatic jointed

vitreous lava at the

perlite quarry

Contact of perlite

and rhyolite tuff at

the perlite quarry

Perlite develops in

the course of

hydration of obsidian

Perlite consists of

pearl-like small

spheroid fragments

Pearl textured perlite

Fresh discontinuity

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at the perlite quarry on perlite

Selected literatures

Balogh K. - Szebényi L. 1947: Pálháza (Abaúj-Torna vm.) környékének földtani viszonyai. - A Magyar Állami

Földtani Intézet évi jelentése 1945-ről, II., 61-64.

Bognár L. 1987: Ásványhatározó. – Gondolat Kiadó, Budapest, p. 478.

Szakáll S. (szerk.) 1996: 100 magyarországi ásványlelőhely. – Minerofil Kiskönyvtár II., p. 139.

Szakáll S. 2008: Barangolás az ásványok világában. – Debrecen, p. 120.

Szakáll S. – Jánosi M. 1995: Magyarország ásványai. Kiállításvezető. – Miskolc, 27-36.

29. Rudabánya, iron ore quarries

The quarryies, which are situated to the northeast to Rudabánya, can be approached from several directions, but

the easiest is, if we turn right on the road which passes the „Érc-és Ásványbányászati Múzeum” towards

Szendrő (Fig. 5.6.1.). Turning to the left on a dirt road, before the board, which signs the end of locality, we can

reach the quarries named Polyánka, Lónyai and Andrássy III mine parts. Going 300m to Szendrő we deviate

again to the left side, to the road, which leads to Alsótelekes and turn to the dirt road, which leads to the left,

immediately after the branching and we get to the Andrássy I mine part. After taking further 500 m on the road,

a few meters away the old transformer house there’s a dirt road on which we can get down to the Andrássy II

and „Villanytető” mine parts. 800 m after the old transformer house turning to the left on the so-called „majom

telep” branching on the asphalted road, then turning down to the right, we can get to the Vilmos mine part on a

dirty road. The geographical coordinates of the Andrássy II. mine part are: 48°23'9.75"N, 20°37'46.49"E (Fig.

5.6.2.).

Fig. 5.6.1. Geographical

position of the Andrássy II

mine at Rudabánya

Fig. 5.6.2. Topographical

map of Rudabánya and its

environs

Fig. 5.6.3. Geological map

of Rudabánya and its

environs

The iron ore plant developed in dolomite to the impact of hydrothermal meta-somatic processes. Because of

this, mostly siderite ore formed with masses of barite at some places and with sulfide minerals. Later, the result

of extensive weathering near the surface oxidation and cementation belt formed in which the limonite and

spherosiderite ores are dominant. Minerals can be found at every part of the quarry system. Rudabánya is the

richest mineral collecting site in Hungary. The number of mineral species have been detected here is 95 so far

(Fig. 5.6.3.).

The most frequent minerals which can be collected in the Andrássy II. mine part are the following:

Azurite: azure, stout veins, crusts, or 2-4 mm tabular and squat crystals which surface weathered into malachite

in most cases.

Barite: colourless, white, stout, 1-3 mm tabular crystals in the cavities

Cerussite: colourless, grey, polished diamond veins, nests, 1-3 mm crystals in the nests.

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Cinna barite: dark red, cherry red, earthy or stout nests.

Goethite: rusty, tan, earthy, cell-like, stout, or black, bright surfaced crusts, spherical- reniform aggregates.

Malachite: green, powdery, crust-like, or pin-radial, mostly 2-4 mm- sized spherical sets, or dark green

columnar crystals.

Siderite: light brown, stout, 1-3 mm romboeders, spherical aggregates in the cavities.

Native copper: wiry, moss-like, hair-like sets.

View of Andrássy II

mine at Rudabánya

Limonite blocks in

the Andrássy II mine

at Rudabánya

A part of mine wall

built up from

ironstone at

Andrássy II mine at

Rudabánya

Cavity in limonite

encrusted by calcite

crystals at Andrássy

II mine at Rudabánya

Malachite crystals

on limonite at

Andrássy II mine at

Rudabánya

Giant limonite block

in front of the

Rudabánya Mining

Museum

Native copper from

at Andrássy II mine

at Rudabánya

Spheroidal goethite

in a cavity of

ironstone at

Andrássy II mine at

Rudabánya

Spheroidal goethite

in cavity of ironstone

(other view)

Siderite crystals

from Andrássy II

mine

Iron-rich, dark brown

siderite from

Andrássy II mine

Massive barite from

Andrássy II mine

Azurite crystals on

limonite from

Andrássy II mine at

Rudabánya

Malachite and calcite

crystals collected at

Andrássy II mine at

Rudabánya

Goethite and

malachite crystals

on limonite from

Andrássy II mine at

Rudabánya

Ironstone with high

iron-content from

Andrássy II mine at

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Rudabánya

Selected literatures

Bognár L. 1987: Ásványhatározó. – Gondolat Kiadó, Budapest, p. 478.

Földessy J. - Németh N. - Gerges A. 2010: A rudabányai színesfém-ércesedés újrakutatásának előzetes földtani

eredményei. – Földtani Közlöny, 140(3). 281-292.

Grill J. - Kovács S. - Less Gy. - Réti Zs. - Róth L. 1984: Az Aggtelek-Rudabányai-hegység földtani felépítése és

fejlődéstörténete. – Földtani kutatás: földtani szakmai folyóirat, 27(4), 49.

Juhász Á. 1987: Évmilliók emlékei. – Gondolat Kiadó, Budapest, 162-166., 459-461.

Szakáll S. (szerk.) 1996: 100 magyarországi ásványlelőhely. – Minerofil Kiskönyvtár II., p. 139.

Szakáll S. 2008: Barangolás az ásványok világában. – Debrecen, p. 120.

Szakáll S. – Jánosi M. 1995: Magyarország ásványai. Kiállításvezető. – Miskolc, 36-43.

30. Salgótarján-Somoskőújfalu, Eresztvény basalt quarry

After crossing Somoskőújfalu Salgótarján and leaving Eresztvény Resort there is bifurcation 350 m to the left,

which leads to Eresztvény basalt quarry. There’s a huge abandoned quarry system which consists of several

levels (Fig. 5.7.1.). The locality’s geographical coordinates are: 48°09'2123"N, 19°51'44.71"E (Fig. 5.7.2.).

Fig. 5.7.1. Geographical

position of the Eresztvény

quarry at Salgóbánya

Fig. 5.7.2. Topographical

map of Salgóbánya and its

environs

Fig. 5.7.3. Geological map

of Salgóbánya and its

environs

There have been a violent, freatomagmatic volcanic activity at the Karancs-Medves region during the Pliocene,

about 8 million years ago, when lava were produced from a number of small eruption centers. Because of the

volcanic activity basalts and basaltic cinders formed, covering large areas. The vocanic superstructures are

partly or totally decayed by now. Generally, only channel casts, more or less cylindrical shape lava masses

cooled in the volcanic conduits, can be examined. It is characteristic feature of these lavas that they conatin

large mineral- and rock inclusions, which are originated from almost 70 km depth magma chamber. The

inclusions refer to that the plume was very fast in the magma chambers, because in the case of opposite situation

the inclusions would be dissolved. This channel cast basalts can be studied at the Eresztvény basalt quarries. In

the groundmass of the basalt, more cm peridote, amphibole and plagioclase-crystals can be found. While calcite,

siderite and other additional minerals are situated in the bladder cavities of the rock (Fig. 5.7.3.).

The most frequent minerals which can be collected in the quarry of the Eresztvény:

Aragonite: colourless, white, 1-3 mm pin crystals and radial sets.

Augit: black particles in the basalt,2-4 mm crystals in the basalt tuff

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Forsterite: green, glass gloss particles in the basalt, 1.3 mm, squat crystals in the basalt tuff

Calcite: white romboeders and spheroidal crusts.

Phillipsite: white, 1-2 mm crystals, together fused groupd and incrustings.

Pirrhotine: brown, metallic luster, cm reaching stout nets.

Siderite: maximum 3 mm diametered, spheroidal sets in the bladder cavities of the basalt

View of the smaller

strip pit of the

Eresztvény quarry at

Salgóbánya

Entrance of the

Eresztvény quarry at

Salgóbánya

Western part of the

strip pit, Eresztvény

quarry, Salgóbánya

Scorious basalt in the

Eresztvény quarry at

Salgóbánya

Thin bedded basalt

and scorious basalt

in the Eresztvény

quarry at

Salgóbánya

Alternating of basalt

lava and basalt

scoria; Eresztvény

quarry, Salgóbánya

Fragmented basalt in

the Eresztvény

quarry at Salgóbánya

Arcuate bended,

bedded basalt in the

Eresztvény quarry at

Salgóbánya

Debris of basalt in

the Eresztvény

quarry

Thick lava beds in

the Eresztvény

quarry

Scorious basalt block

in the Eresztvény

quarry

Scorious basaltic

lava block in the

Eresztvény quarry

Vesicles refer to the

significant volatile

content of the lava in

the Eresztvény

quarry at Salgóbánya

Elongated vesicles in

basalt at the

Eresztvény quarry

Detail of a vesicular

basalt block in the

Eresztvény quarry

Vesicular basalt

blocks in the

Eresztvény quarry at

Salgóbánya

Inner part of a

freshly broken

vesicular basalt block

in the Eresztvény

Lherzolite xenolith in

basalt in the

Eresztvény quarry at

Salgóbánya

Giant olivine crystal

in basalt in the

Eresztvény quarry at

Salgóbánya

Giant amphibole

crystal in basalt in

the Eresztvény

quarry at

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quarry Salgóbánya

Giant feldspar crystal

in basalt in the

Eresztvény quarry at

Salgóbánya

Minerals occur in the

vesicles of scorious

basalt dominantly

Small vesicle

encrusted by calcite

crystals in basalt in

the Eresztvény

quarry at Salgóbánya

Selected literatures

Bognár L. 1987: Ásványhatározó. – Gondolat Kiadó, Budapest, p. 478.

Budai T. – Gyalog L. 2009: Magyarország földtani atlasza országjáróknak. – Budapest, 170.

Juhász Á. 1987: Évmilliók emlékei. – Gondolat Kiadó, Budapest, 436-438.

Szakáll S. (szerk.) 1996: 100 magyarországi ásványlelőhely. – Minerofil Kiskönyvtár II., p. 139.

Szakáll S. 2007: A Karancs, a Medves és a Cseres-hegység ásványtani jellemzése. – In: Kiss G. (szerk.) 2007: A

Karancs- Medves és a Cseres-hegység Tájvédelmi Körzet. Nógrád és Gömör határán. – Eger, 51-56.

Szakáll S. 2008: Barangolás az ásványok világában. – Debrecen, p. 120.

Szakáll S. – Jánosi M. 1995: Magyarország ásványai. Kiállításvezető. – Miskolc, 56-61.

31. Sukoró, Rigó Hill, granite quarry

The granite of Velence Mountains are exposed in several smaller-bigger quarries (Fig. 5.8.1.). One of them is

the Rigó Hill quarry in the vicinity of Sukoró which is the most varied one among all. The quarry is situated 1,5

km away from Sukoró to the West. The mine can be approached along the road which leads to the weekend

houses. The geographical coordinates: of the locality are: 47°14’15.58”N, 18°34’59.68”E (Fig. 5.8.2.).

Fig. 5.8.1. Geographical

position of the quarry at

Rigó Hill

Fig. 5.8.2. Topographical

map of Sukoró and its

environs

Fig.5.8.3. Geological map

of Sukoró and its environs

The Velence Mountains is built up from Carboniferous granites dominantly, which formed during the formation

of the Variszkusz Mountain system. This rock is exposed in the quarry at Sukoró. More version of The granite

appears there in great variety. There:are aplits, pregmatits, and fine grained granite gravel (granite rubblestone)

also can be found at the locality.

The minerals, which can be collected there, are firstly the rock-forming minerals themselves, and secondly those

minerals which can be found in the cavities of the pegmatite veins (Fig. 5.8.3.).

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Albite: 2-3 mm thick tabular crystals.

Clinochlore: dirty green, green, dust-like sets, on albite. quartz and orthoclase

Quartz: white, grey, sometimes cairngorm natured squat columnar crystals, which’s size can reach the 2-4 cm

Orthoclase: pale red, 2-4 cm columnar crystals.

View of the northern

side of the quarry at

Rigó Hill

Carboniferous

granite is exposed in

the quarry at Rigó

Hill

Granite block in the

quarry at Rigó Hill

Granite aplite in the

quarry at Rigó Hill

Granite rubblestone

arose in the course of

weathering of the

granite

Selected literatures

Bognár L. 1987: Ásványhatározó. – Gondolat Kiadó, Budapest, p. 478.

Juhász Á. 1987: Évmilliók emlékei. – Gondolat Kiadó, Budapest, 367-370.

Kubovics I. 1958: A sukorói Meleghegy hidrotermás ércesedése. - Földtani Közlöny, 88(3). 299-314.

Nagy B. 1967: A velencei-hegységi gránitos kőzetek ásvány-kőzettani, geokémiai vizsgálata. - Földtani

Közlöny, 97(4). 423-436.

Szakáll S. – Jánosi M. 1995: Magyarország ásványai. Kiállításvezető. – Miskolc, 82-87.

Szakáll S. (szerk.) 1996: 100 magyarországi ásványlelőhely. – Minerofil Kiskönyvtár II., p. 139.

Szakáll S. 2008: Barangolás az ásványok világában. – Debrecen, p. 120.

32. Szarvaskő, Újhatár Valley, Tóbérc-Mine, gabbró quarry

On the road from Eger towards Szarvaskő you have to deviate to the right from the road at the last big curve

before the locality. The Eger stream which flows next to the road can be crossed only on foot. And after about

150 m you reach the quarry which can be seen from the road too (Fig. 5.9.1.). The geographical coordinates of

the quarry: 48°00'04.88"N, 20°19'16.27"E (Fig. 5.9.2.).

Fig. 5.9.1. Geographical

position of the Tóbérc

quarry at Szarvaskő

Fig. 5.9.3. Geological map

of Szarvaskő and its

environs

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Fig. 5.9.2. Topographical

map of Szarvaskő and its

environs

Both side of the basaltic range which is situated at the south-western part of the Bükk Mountains accompained

by gabbro intrusions which intruded into and got stuck in different Jurassic age sediment series. The gabbro

have been used for road and railway construction. There have been five large and numerous smaller quarries

along the valley of the Eger stream. Among the above mentioned quarries the most significant is the Tó-bérc

quarry (also known as Forgalmi quarry) from geological point of view. The quarry is situated at the beginning of

the Újhatár valley, east to Szarvaskő. The quarry, where mining has been finished around fifty years ago,

contains the most comprehesive geological informations about the region.

A gabbro intrusion, which intruded into Middle Jurassic age deepsea sediments about 166 million years ago, is

exposed by the quarry. The 1500 ºC temperature magma heated up its environment and formed a muscovite-

hornfels at the contact zone, melting the sediments. The huge sediment blocks which got into the magma partly

have been assimilated (biotite-gabbro), partly have been melted only, which led to the formation of a special

compound rock type (garnet-plagioclase).

The certain walls of the quarry serve with different sights.

At the western part of the northern wall there is an S-shaped emerging crest which consists of plagioclase

feldspar – almost pure albite – formed from the sediments melted along the contact zone. Its original colour is

darkgrey but whitens among subaerial circumstances. Going outward the grade of metamorphism is weaken

permanently and the grain-size of the minerals decrease. The original, not metamorphosed sediments can be

traced over the mine’s wall, only. At the middle and the eastern part of the northern wall and in the case of the

eastern wall different gabbro versions can be observed. There are white coloured veins in them consisting of

prehnite-quartz-calcite. At the middle of the northern wall of the quarry a white-gray rock-body can be

observed. That is the granatiferous quartzplagioclasite. Its main rock-forming minerals are the albite and the

quartz with small redish-brown garnet crystals (almandine). At the eastern wall there have been hard, lumpy

fractured, greenish-gray gabbro mined. There is a steep, normal fault dipping to the south at the upper section of

the southern wall. The wall itself consists of angular rock-debris. This is the the so called fault breccia which is

situated at the boundary of the foult and the intrusion. At the contact zone muscovite-hornfels has been formed

(Fig. 5.9.3.).

The minerals which can be collected at the Tóbérc-quarry of Újhatár-völgy, Szarvaskő are the following:

Almandine: pink at the contact 1-6 cm massive aggregations, deep red, 2-6 mm crystals in the gabbro.

Heulandite: colourless, 1-2 cm squat crystals connecting to the calcite filled veins.

Hornblende: black, 2-4 cm columnar-fibrous crystals in the gabbro.

Calcite: white coloured veins, encrustations in cavities, or 1-3 mm crystals

Chalcopyrite: 1-3 mm grains, nests with pirrhotin and dissaminated in the gabbro

Laumontite: white, nacreous, columnar-radial crystal aggregates in the fissures.

Muscovite: argent, 2-4 mm flakes in the shale of the contact zone.

Pyrite: mm disseminations, veins, crystals.

Pirrhotin: 1-4 mm nests, lamellas together with chalcopyrite

Plagioclase: light green, off-white, 1-3 cm crystals in the gabbro

Prehnite: white, light green radial sets, 1-3 mm tabular crystals in the cavities.

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View of the Tóbérc

quarry, Újhatárvölgy,

from the village

Szarvaskő

The beginning;

bridge over the Eger

stream

You have to cross the

bridge of the Eger

stream to reach the

locality

View of the

abandoned quarry

from the south

On the way to the

Tóbérc quarry.

Outcrop of Jurassic

age shale along the

rails

Be careful when

cross the railway

following the route to

the quarry!

The pathway leading

to the quarry starts

among the trees

Northern wall of the

Tóbérc quarry

Eastern wall of the

Tóbérc quarry

Welded shale at the

upper part of the

Tóbérc quarry

The characteristic

rock of the Tóbérc

quarry is the Jurassic

age gabbro

Gabbro blocks in

strip pit of the

Tóbérc quarry

Closer view of the

gabbro which is a

holocrystalline,

plutonic rock

Gabbro pegmatite

also can be found at

the quarry in great

quantities

Contact hornfels at

the margin of

magma and shale at

the northern part of

the quarry

Black, welded shale

close to the former

magmatic intrusion

Welded shale block

at the strip pit of

Tóbérc quarry

Granatiferous

quartzplagioclasite

intrusion at the

northern part of the

quarry

Granatiferous

quartzplagioclasite

intrusion in gabbroid

magmatic body

The granatiferous

quartzplagioclasite

is a light coloured

felsic rock

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Granate crystals in

granatiferous

quartzplagioclasite of

the Tóbérc quarry

Fault breccia at the

eastern part of the

quarry

Large plagioclase

aggregate in gabbro

Fissure filled with

plagioclase at the

margin of the gabbro

body

Fissure filled with

plagioclase at the

margin of the

gabbro body; closer

view

Plagioclase filled

thin fissures in

gabbro at Tóbérc

quarry

Fault plane at the

eastern part of the

quarry

Contact metamorphic

rocks can be

observed at the

southern part of the

quarry

The muscovite is one

of the rock-forming

mineral of contact

metamorphic rocks

of the Tóbérc quarry

Selected literatures

Bognár L. 1987: Ásványhatározó. – Gondolat Kiadó, Budapest, p. 478.

Juhász Á. 1987: Évmilliók emlékei. – Gondolat Kiadó, Budapest, 142-146.

Pelikán P. (szerk.) 2005: A Bükk hegység földtana. Magyarázó a Bükk-hegység földtani térképéhet (1:50 000).

– Budapest, 89-92.

Szakáll S. (szerk.) 1996: 100 magyarországi ásványlelőhely. – Minerofil Kiskönyvtár II., p. 139.

Szakáll S. 2008: Barangolás az ásványok világában. – Debrecen, p. 120.

Szakáll S. – Jánosi M. 1995: Magyarország ásványai. Kiállításvezető. – Miskolc, 18-25.

Szentpétery Zs. – Emszt K. 1930: Kőzettípusok Szarvaskőről. – Földtani közlöny, 60(1-2). 57-67.

33. Szokolya-Királyrét

The locility is situated three kms from Szokolya to north-northwest, at the north-east side of the Vár Hill, where

strongly wathered andesite tuff crops out along the tourist pathway (Fig. 5.10.1.). Well-developed garnet

crystals appear in the soft, weathered rock, and also in the alluvium of the Török stream nearby. The locality can

be approached by train, by bus, and by car from Kismaros. The area’s geographical coordinates are:

47°53'04.66"N, 18°59'02.53"E (Fig. 5.10.2.).

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Fig. 5.10.1. Geographical

position of the exposure at

Szokolya-Királyrét

Fig. 5.10.2. Topographical

map of Szokolya-Királyrét

and its environs

Fig. 5.10.3. Geological

map of Szokolya-Királyrét

and its environs

Andesites, and andesite piroclastics can be found in the vicinity of Szokolya. These rocks are characteristic to

the entire Börzsöny Mountains. The piroclasts are originated from andesitic volcanic activity. These came up

during the volcanism which is connected to the Carpathians’ protrusion which took place during the Miocene.

Strongly weathered, little sag, garnet-biotite andesite can be found at the collecting site, which from the minerals

can be easily picked out (Fig. 5.10.3.).

The following minerals can be collected at the locality:

Almandine: deep red, brownish red, 2-8 mm crystals.

Augite: black: 2-4 mm squat crystals.

Biotite: black (if weathered brown), 1-3 mm-es hexagonal tables.

Hornblende: black, 1-3 mm prisms.

Quartz: grayish white, white, a few mm squat crystals.

Magnetite: black, 1-2 mm octahedrons.

Plagioclase: white, 1-3 mm columnar crystals.

View of the altered andesite

tuff close to Szokolya-

Királyrét

Garnet crystals can be

commonly found in the

andesite tuff at Szokolya-

Királyrét

Altered andesite tuff is a

chaotic structured, soft rock

Garnet crystals can

be easily collected

from the debris of

the andesite tuff

Selected literatures

Bognár L. 1987: Ásványhatározó. – Gondolat Kiadó, Budapest, p. 478.

Juhász Á. 1987: Évmilliók emlékei. – Gondolat Kiadó, Budapest, 414-423.

Kiss M. 1924: A Szokolya és Nógrád közötti terület andesites kőzetei I-II. - Bányászati és kohászati lapok, 57,

189-193, 207-210.

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Lengyel E. 1956: A Börzsönyhegység Nógrád-Szokolya környéki területének újrafelvétele. – A Magyar Állami

Földtani Intézet évi jelentése 1954-ről, 1, 105-123.

Szakáll S. (szerk.) 1996: 100 magyarországi ásványlelőhely. – Minerofil Kiskönyvtár II., p. 139.

Szakáll S. 2008: Barangolás az ásványok világában. – Debrecen, p. 120.

Szakáll S. – Jánosi M. 1995: Magyarország ásványai. Kiállításvezető. – Miskolc, 62-67.

34. Tapolca, Halyagos Hill

The Halyagos-hegy is situated 7 km away from Tapolca to the East (Fig. 5.11.1.). Half of it is occupied by an

abandoned basalt quarry. The quarry can be easily reached from Tapolca by car. The mine has got two floors. At

its lower part petrological and volcanological curiosities (e.g pepperit) can be collected, while in the case of the

upper level there are several mineral species can be found in the cavities of the rock. The geographical

coordinates of the locality are: 46°53’01.00N, 17°31’10.44”E (Fig. 5.11.2.).

Fig. 5.11.1. Geographical

position of the Halyagos

Hill quarry

Fig. 5.11.2. Topographical

map of Halyagos Hill and

its environs

Fig. 5.11.3. Geological

map of Halyagos Hill and

its environs

The Pliocene age basalt and its tuff are wide spread in the Tapolca basin. These basalt and basalt tuff build up

those spectacular volcanic cones, which material had been used for road construction, and building stone for

decades. The Halyagos-hill’s huge, two floored quarry is among the mines which produced the above mentioned

basaltic rocks. The basalt contains mainly augite and forsterire which formed during the main crystallization of

the magma. The minerals of hydrothermal processes are characteristic to the vesicles. The rock-forming silicates

(augite, hornblende, plagioclases); the oxides (magnetite, hematite, ilmenite) and the apatite can be observed in

the first period of the formation. The carbonates were crystallized later (calcite, aragonite and the zeolites

(phillipsite, chabazite, natrolite, tetranatrolite, gonnardite, gmelinite, thomsonite). The latter ones are the real

curiosities of the basalt’s cavities, because of their varied appearence (Fig. 5.11.3.).

The most frequent minerals of the Halyagos hill are the following:

Apatite: colourless, mm with needle aggregates.

Apofillite: clear, 1-3 mm columns or bipyramids.

Gonnardite: colourless, translucent or white crystals; spheres of acicular aggregates.

Ilmenite: black thin tabular or lamellar crystals.

Chabazite: white or colourless, mm, romboeders

Calcite: white or colourless, maximum 5 mm romboeders

Magnetite: black, 1-2 mm octahedral crystals.

Natrolite: colourless or white, 1-2 mm spheres of acicular aggregates.

Phillipsite: colourless and white, squat crystals.

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Tetranatrolite: colourless or white, 1-2 mm elongated columnar crystals. Its segregation from the natrolite is

possible using instrumental examinations only.

View of the strip pit of

the Halyagos Hill

quarry

Detail of the lower

strip pit of the

Halyagos Hill quarry

Basalt is the dominant

rock of the Halyagos

Hill quarry

Peperite wall at the

northern side of the

lower strip pit at

Halyagos Hill

The peperite

consists of lava

fragments and

welded

sediments

which formed

during

underwater

volcanic

activity

Dark coloured lava

blocks and yellowish

welded sediments

(peperite) at the

entrance of the lower

strip pit at Halyagos

Hill

Lava blocks are

cemented by the

mixture of fine-

grained volcanic ash

and marine sediments

Giant vesicles are at

the upper strip pit of

the Halyagos Hill

quarry

The giant, rounded

vesicles refer to rapid

solidification of the

lava

Giant vesicles

can be found in

concentric

parted basalt

Natrolite crystals in

the vesicle of basalt

collected at the upper

strip pit of the

Halyagos Hill quarry

Acicular natrolite

crystals in the vesicle

of basalt; closer view

Selected literatures

Bognár L. 1987: Ásványhatározó. – Gondolat Kiadó, Budapest, p. 478.

Budai T - Csillag G. (szerk.) 1999: A Balaton-felvidék földtana. Magyarázó a Balaton-felvidék földtani

térképéhez, 1:50 000. – Budapest, p. 257.

Juhász Á. 1987: Évmilliók emlékei. – Gondolat Kiadó, Budapest, 337-365.

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Szakáll S. (szerk.) 1996: 100 magyarországi ásványlelőhely. – Minerofil Kiskönyvtár II., p. 139.

Szakáll S. 2008: Barangolás az ásványok világában. – Debrecen, p. 120.

Szakáll S. – Jánosi M. 1995: Magyarország ásványai. Kiállításvezető. – Miskolc, 88-97.

35. Telkibánya, mine dump of Vörösvíz drift gallery

The Vörösvíz drift gallery is situated to the east - northeast to Telkibánya where we can find one of the most

famous gold exploration site of the region (Fig. 5.12.1.). It can be approached only on foot. The yellow tourist

sign, which curves directly next to the entrance of the former drift gallery starts from Mathias king’s well.

Really varied mineral associations can be collected during the way in the forest, at the smaller spolis and at the

horpas. The geographical coordinates of the locality are: 48°29’23.70”N, 21°24’11.65”E (Fig. 5.12.2.).

Fig. 5.12.1. Geographical

position of the Vörösvíz

drift gallery

Fig. 5.12.2. Topographical

map of Telkibánya and its

environs

Fig. 5.12.3. Geological

map of Telkibánya and its

environs

The rocks of the area belong into the Telkibánya Kalimetasomatic Member of the Baskó Andesite Formation.

The andesite itself, regarding its composition, is a felsic pyroxene-andesite, which was altered in several ways

due to the postvolcanic activity. Beside bentonitisation, oxidation and propylitisation due to potassium rich

fluids metasomatisation also altered the original rock. This was the result of the formation of varied rock types,

like kalitrachite, pseudotrachite, kalimetasomatit. Their K2O content often reach the 9 -12 percent.

During the intervals of the volcanic activity and after the finishing of that great variety of postvolcanic processes

took place alternating the mineral composition of the original rocks and on the other hand silica, carbonate,

metallic and non-metallic minerals seceded from the hotwater solutions.

These processes resulted the formation of the gold-ore mineral deposits of the Carpathian Basin. The most

characteristic occurrences of these mineral deposits can be found int he vicinity of Telkibánya (Fig. 5.12.3.).

The following minerals can be collected along the yellow sign leading to the mine dumps:

Akantite: black massive aggregations, mm elongated-columnar, sometimes acicular crystals in the cavities of the

vein quartz

Galena: cm disseminations, veins, 1-2 mm hexahedrals in the cavities

Gypsum: colourless, 1-3 mm fibrous or radial aggregations.

Goethite: rusty-brown patches, encrustments, spherical aggregations.

Hematite: fulvous, earthy masses, coatings.

Jarosite: yellow, earthy coating, rarely mm long rhombohedrals

Quartz: the dominat mineral of the vein quartz 1-3 cm crystals in the cavities amethyst, smoky-quartz,

bergcrystal and the morion varieties are frequent in the cavities. Sometimes you can find even larger crystals (5-

15cm) in the altered rocks, which can be found in the soil after weathering of the rock.

Markazite: it appears as disseminations, veins, encrustings.

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Opal: brown, yellow, massive aggregations in the vein quartz.

Orthoclase (adularia): white, colourless, more cm massive aggregations, 1-3 mm rhombohedral-like crystals

with quartz in the fissures

Pirargirite, proustite: dark cherry red, or lighter red 1-3 mm aggregations, massive-columnar crystals. Generally

they can be distinguished from one another with instrumental examinations

Pyrite: disseminations, veins, or 1-3 mm crystals

Sphalerite: dark brown aggregations, disseminations, and1-3 mm tetrahedrals in cavities.

Minerals can be

collected from debris

close to the trail

leading to Vörösvíz

drift gallery

Quartz and quartz

varieties in a vesicle

of an rhyolite block

collected along the

trail to Vörösvíz drift

gallery

Grown-up quartz

crystals in an

elongated vesicle

from Telkibánya

Groups of quartz

crystals in rhyolite

from Telkibánya

Small quartz crystals

on chalcedony crust

from Telkibánya

Chalcedony crust

with small quartz

crystals from

Telkibánya

Grown-up quartz

crystals formed in

cavity of rhyolite

from Telkibánya

Sceptre-quartz in a

rhyolite geode from

Telkibánya

Micron sized quartz

crystals encrusting a

piece of rhyolite

Chalcedony covered

by micron-sized

quartz crystals

Chalcedony

encrusted by micron-

sized quartz crystals

Chalcedony

encrusted by micron-

sized quartz crystals

(closer view)

Laminar and drop-

stone like

chalcedony

Rhyolite with a thin

agate crust

Rare occurrence of

honey opal in the

cavity of a silicified

rhyolite, from

Telkibánya

Selected literatures

Bognár L. 1987: Ásványhatározó. – Gondolat Kiadó, Budapest, p. 478.

Horváth J. – Zelenka T. 1997: A telkibányai nemesfém-ércesedés legújabb bányaföldtani adatai és értékelése –

Földtani Közlöny, 127(3-4), 405-430.

Juhász Á. 1987: Évmilliók emlékei. – Gondolat Kiadó, Budapest, 172-173., 463-470.

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Komlóssy Gy. 1997: Nemesfém kutatási lehetőségek Telkibánya környékén. – Földtani kutatás: földtani

szakmai folyóirat, 34(2), 5-7.

Szakáll S. (szerk.) 1996: 100 magyarországi ásványlelőhely. – Minerofil Kiskönyvtár II., p. 139.

Szakáll S. 2007: A Tokaji-hegység ásványtani jellemzése. – In: Baráz Cs. – Kiss G. (szerk.) 2007: A Zempléni

Tájvédelmi Körzet. Abaúj és Zemplén határán. – Eger, 45-54.

Szakáll S. 2008: Barangolás az ásványok világában. – Debrecen, p. 120.

Szakáll S. – Jánosi M. 1995: Magyarország ásványai. Kiállításvezető. – Miskolc, 27-36.

Szepesi J. – Kozák M. 2008: A telkibányai Cser-hegy-Ó-Gönc riolit-perlit vonulat fáciesgenetikai és

paleovulkáni rekonstrukciója. – Földtani Közlöny, 38(1), 61-83.

Fájlok

3_1_mezozoic_sirok_recsk.ppt

3_3_gyongyosoroszi_matraszentimre.ppt

3_4_miocene_andezite.ppt

3_8_sedimentary_minerals.ppt

3_7_paradsasvar.ppt

1_Minerals_of_the_geography_department_collection.ppt

3_5_Miocene_rhyolite.ppt

2_ock_samples_of_the_geography_department_collection.ppt

3_2_recsk.ppt

3_6_paradfurdo.ppt